Oregon: Individual County Chronologies

Oregon Atlas of Historical County Boundaries

John H. Long, Editor; Peggy Tuck Sinko, Associate Editor; Emily Kelley, Historical Compiler; Laura Rico-Beck, GIS Specialist and Digital Compiler; Peter Siczewicz, ArcIMS Interactive Map Designer; Robert Will, Cartographic Assistant

Copyright The Newberry Library 2007

BAKER

22 Sep 1862
BAKER created from WASCO. (Ore. Laws 1862, 2nd reg. sess., p. 112)
14 Oct 1864
BAKER lost to creation of UNION. (Ore. Laws 1864, 3rd reg. sess., p. 37)
20 Oct 1870
BAKER gained from GRANT. (Ore. Laws 1870, 6th reg. sess., pp. 167-168)
19 Oct 1872
BAKER lost to GRANT. (Ore. Laws 1872, 7th reg. sess., pp. 34-35)
16 Oct 1878
BAKER gained from GRANT and UNION; gained part of the overlap area between GRANT and UNION. (Ore. Special Laws 1878, 10th reg. sess., pp. 118-120)
01 Apr 1887
BAKER lost to creation of MALHEUR. (Ore. Laws 1887, gen., 14th reg. sess., pp. 138-141)
01 Mar 1901
BAKER gained from UNION. (Ore. Laws 1901, 21st reg. sess., pp. 435-438)
23 Feb 1915
BAKER gained from WALLOWA. (Ore. Laws 1915, gen., 28th reg. sess., ch. 134/pp. 145-146)
06 Feb 1931
BAKER exchanged with MALHEUR. (Ore. Laws 1931, gen., 36th reg. sess., ch. 18/pp. 26-28)

BENTON

23 Dec 1847
BENTON created by the Provisional Legislature of Oregon Territory from area formerly part of POLK. On 20 December 1847 the Journal of the Provisional Legislature recorded the passage of an act to redefine the boundaries of POLK. No such act appears within the session laws, but the definition of BENTON depends on an earlier change having been made to the south line of POLK. (Ore. Terr. Laws, general and local, 1843-1849, p. 50; Holman, 28-30; Oregon Archives, 237)
15 Jan 1851
BENTON lost to creation of Non-County Area 4 when the county's southern line redefined. This change apparently made in preparation for creation of UMPQUA (extinct) on 24 January 1851, and creation of LANE on 28 January 1851. (Ore. Terr. Laws 1850, 2nd sess., p. 34)
14 Feb 1859
BENTON became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
20 Feb 1893
BENTON lost to creation of LINCOLN. (Ore. Laws 1893, gen., 17th reg. sess., pp. 68-77)
15 Feb 1923
BENTON gained from LANE. (Ore. Laws 1923, gen., 32nd reg. sess., ch. 92/pp. 129-131)
03 Mar 1927
BENTON lost to LINCOLN when boundary was redefined to run along range line. (Ore. Laws 1927, gen., 34th reg. sess., ch. 278/pp. 350-351)
14 Apr 1949
BENTON gained from LINCOLN. (Ore. Laws 1949, gen., 45th reg. sess., ch. 401/pp. 593-596)

CHAMPOEG (see MARION)

CLACKAMAS

05 Jul 1843
CLACKAMAS DISTRICT created. CLACKAMAS was one of four original counties created by the Provisional Legislature of Oregon Territory. Included parts of present Oregon, Washington, Idaho, Montana and Canada. (Oregon Archives, p. 26)
27 Jun 1844
CLACKAMAS DISTRICT lost to creation of Non-County Area 1 when the CLACKMAS boundary was redefined to run along the Columbia River. (Ore. Terr. Laws, general and local, 1843-1849, p. 74)
19 Dec 1845
CLACKAMAS DISTRICT gained from CHAMPOEG DISTRICT (now MARION). Boundary between CLACKAMAS DISTRICT and TUALITY DISTRICT (now WASHINGTON) redefined to run "along the middle of the main channel of the Willamette River to the center of the Columbia River at the upper mouth of the Willamette." (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
22 Dec 1845
CLACKAMAS DISTRICT renamed CLACKAMAS County; no change in boundaries [not mapped]. (Ore. Terr. Laws, general and local, 1843-1849, p.35)
15 Jun 1846
CLACKAMAS lost to British North America when the Oregon Boundary Treaty between the United States and Great Britain established the northern boundary of Oregon Territory at 49 degrees north latitude. (Hayes, 134, 171-174; Parry 100:40-42; Van Zandt, 18)
02 Mar 1853
CLACKAMAS lost to creation of Washington Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)
11 Jan 1854
CLACKAMAS lost to creation of WASCO. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
22 Dec 1854
CLACKAMAS gained from WASHINGTON and YAMHILL; lost to creation of MULTNOMAH. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 29)
30 Jan 1856
CLACKAMAS gained from MARION. (Ore. Terr. Laws 1855-1856, 7th reg. sess., p. 50)
14 Feb 1859
CLACKAMAS became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
17 Oct 1860
CLACKAMAS gained from YAMHILL. (Ore. Laws 1860, 1st reg. sess., p. 47)
17 Oct 1862
CLACKAMAS gained from WASHINGTON. (Ore. Laws 1862, 2nd reg. sess., p. 98)
20 Feb 1893
CLACKAMAS lost small area (part of the town of Sellwood) to MULTNOMAH. (Ore. Laws 1893, gen., 17th reg. sess., pp. 78-79)
22 Feb 1893
CLACKAMAS exchanged with WASHINGTON. (Ore. Laws 1893, gen., 17th reg. sess., pp. 161-162)
08 Feb 1911
CLACKAMAS boundary with MARION redefined [no change]. (Ore. Laws 1911, gen., 26th reg. sess., ch. 22/p. 39)

CLARK (Wash.)

20 Aug 1845
VANCOUVER DISTRICT (now CLARK, Wash.) created from all of Non-County Area 1; Non-County Area 1 eliminated. (Ore. Terr. Laws 1845, p. 22)
19 Dec 1845
VANCOUVER DISTRICT (now CLARK, Wash.) boundaries with CLACKAMAS DISTRICT, CLATSOP and TUALITY DISTRICT (now WASHINGTON) redefined [no change]. (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
21 Dec 1845
VANCOUVER DISTRICT (now CLARK, Wash.) lost to creation of LEWIS (Wash.). (Ore. Terr. Laws, general and local, 1843-1849, p. 43)
22 Dec 1845
VANCOUVER DISTRICT (now CLARK, Wash.) renamed VANCOUVER County; no change in boundaries [not mapped]. (Ore. Terr. Laws, general and local, 1843-1849, p. 35)
15 Jun 1846
VANCOUVER (now CLARK, Wash.) lost to British North America when the Oregon Boundary Treaty between the United States and Great Britain established the northern boundary of Oregon Territory at 49 degrees north latitude. (Hayes, 134, 171-174; Parry 100:40-42; Van Zandt, 18)
03 Sep 1849
VANCOUVER (Wash.) renamed CLARK (Wash.). (Ore. Terr. Laws 1850, 2nd sess., p. 54)
12 Jan 1852
CLARK (Wash.) lost to creation of THURSTON (Wash.). (Ore. Terr. Laws 1851, 3rd reg. sess., p. 19)
17 Jan 1852
CLARK (Wash.) exchanged with LEWIS (Wash.) when eastern boundary of LEWIS (Wash.) was redefined. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 30)
01 Feb 1853
CLARK (Wash.) exchanged with LEWIS (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40)
02 Mar 1853
CLARK (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

CLATSOP

22 Jun 1844
Provisional Legislature of Oregon Territory authorized the creation of CLATSOP, presumably from the northern and western portions of TUALITY DISTRICT (now WASHINGTON). Introduction and passage of the bill creating CLATSOP appears only within the session minutes for the Journal of the Provisional Legislature (1844), and no act regarding its creation appears in the general or special laws. No boundary description for the new county is given. See 19 December 1845 for the first mappable description of CLATSOP. (Holman, p. 25; Oregon Archives, p. 43)
19 Dec 1845
CLATSOP defined for the first time making it possible to map its 22 June 1844 creation from TUALITY DISTRICT (now WASHINGTON). CLATSOP boundary with VANCOUVER DISTRICT (now CLARK, Wash.) redefined to run along the main channel of the Columbia River. (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
11 Dec 1846
CLATSOP lost to YAMHILL. (Ore. Terr. Laws, general and local, 1843-1849, p. 7)
28 Jan 1852
PACIFIC (Wash.) fully organized, detached from CLATSOP. (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40)
15 Dec 1853
CLATSOP lost to creation of TILLAMOOK. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 6)
15 Jan 1855
CLATSOP redefined; gained from TILLAMOOK, lost to COLUMBIA and WASHINGTON. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 33)
14 Feb 1859
CLATSOP became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
22 Oct 1870
CLATSOP lost to TILLAMOOK. (Ore. Laws 1870, 6th reg. sess., pp. 24-25)
24 Feb 1885
CLATSOP gained from COLUMBIA. (Ore. Special Laws 1885, 13th reg. sess., p. 324)
20 Feb 1891
CLATSOP boundaries redefined, lost to TILLAMOOK. (Ore. Laws 1891, gen., 16th reg. sess., pp. 102-103)
20 Feb 1893
CLATSOP gained from TILLAMOOK. (Ore. Laws 1893, gen., 17th reg. sess., pp. 77-78)
06 Mar 1931
CLATSOP gained from COLUMBIA when boundary was redefined to run along range line. (Ore. Laws 1931, gen., 36th reg. sess., ch. 289/p. 515)
11 Mar 1931
CLATSOP boundaries redefined [no change]. (Ore. Laws 1931, gen., 36th reg. sess., ch. 344/p. 600)

COLUMBIA

16 Jan 1854
COLUMBIA created by Oregon Territory from WASHINGTON. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 32-33)
15 Jan 1855
COLUMBIA's western boundary defined; gained from CLATSOP. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 34)
14 Feb 1859
COLUMBIA became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
24 Oct 1864
COLUMBIA lost to MULTNOMAH. (Ore. Laws 1864, 3rd reg. sess., p. 62)
24 Feb 1885
COLUMBIA boundaries redefined; exchanged with WASHINGTON, lost to CLATSOP and MULTNOMAH. (Ore. Special Laws 1885, 13th reg. sess., p. 324)
15 Oct 1898
COLUMBIA lost to WASHINGTON. (Ore. Laws 1898, 20th spec. sess., pp. 27-28)
25 Feb 1901
COLUMBIA gained from WASHINGTON, exchanged with MULTNOMAH. (Ore. Laws 1901, 21st reg. sess., pp. 126-127)
21 Feb 1903
COLUMBIA lost to WASHINGTON. (Ore. Laws 1903, 22nd reg. sess., pp. 151-152)
06 Mar 1931
COLUMBIA gained from MULTNOMAH, lost to CLATSOP when boundary was redefined to run along range line. (Ore. Laws 1931, gen., 36th reg. sess., ch. 289/p. 515)

COOS

22 Dec 1853
COOS created by Oregon Territory from JACKSON and UMPQUA (extinct); COOS not fully organized, attached to UMPQUA "for judicial purposes." (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 13; Ore. Terr. Rev. Stat. 1853, p. 63)
18 Dec 1855
COOS lost to creation of CURRY. (Ore. Terr. Laws 1855-1856, 7th reg. sess., p. 49)
18 Dec 1856
COOS lost Cammas Prairie to DOUGLAS. (Ore. Terr. Laws 1856-1857, 8th reg. sess., p. 80)
14 Feb 1859
COOS became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
06 Jul 1863
COOS exchanged with DOUGLAS. Act approved 16 October 1862; became effective 6 July 1863. (Ore. Laws 1862, 2nd reg. sess., p. 59)
21 Oct 1864
COOS exchanged with DOUGLAS. (Ore. Laws 1864, 3rd reg. sess., p. 44)
28 Oct 1872
COOS gained from CURRY. (Ore. Laws 1872, 7th reg. sess., pp. 183-184)
19 Oct 1878
COOS gained from DOUGLAS. (Ore. Special Laws 1878, 10th reg. sess., pp. 162-164)
16 Oct 1882
COOS exchanged with DOUGLAS. (Ore. Special Laws 1882, 12th reg. sess., pp. 83-84)
30 Apr 1951
COOS exchanged with CURRY when boundary was redefined to run along township and range lines instead of ridge line. (Ore. Laws 1951, 46th reg. sess., ch. 422/pp. 684-687)
08 May 1951
COOS boundary with CURRY clarified to correct an error in the boundary description of 30 April 1951 [no change]. (Ore. Laws 1951, 46th reg. sess., ch. 494/p. 864)
14 Oct 1983
COOS lost very small area to DOUGLAS. COOS boundary with CURRY redefined to amend description in Oregon Revised Statutes. Became effective 90 days after the end of the legislative session on 16 July [no change]. (Ore. Laws 1983, 62nd reg. sess., ch. 778/pp. 1514-1515)
23 Oct 1999
COOS gained small area from DOUGLAS when boundary was redefined to run along range line. COOS boundary with CURRY was redefined [no change]. (Ore. Laws 1999, 70th reg. sess., ch. 600/pp. 1396-1399)

CROOK

24 Oct 1882
CROOK created from WASCO. (Ore. Special Laws 1882, 12th reg. sess., p. 178)
23 Feb 1885
CROOK gained from GRANT. (Ore. Special Laws 1885, 13th reg. sess., pp. 302-303)
17 Feb 1899
CROOK gained a small area along the John Day River from GILLIAM; lost to creation of WHEELER. (Ore. Laws 1899, 20th reg. sess., pp. 51-55)
27 Feb 1901
CROOK lost small area along the John Day River to WHEELER. (Ore. Laws 1901, 21st reg. sess., pp. 291-292)
12 Dec 1914
CROOK lost to creation of JEFFERSON. (Ore. Laws 1915, gen., 28th reg. sess., Gov. Proc., pp. 9-10)
01 Feb 1917
CROOK lost to creation of DESCHUTES. (Ore. Laws 1917, gen., 29th reg. sess., gov. proc./pp. 5-6; ch. 41/pp. 57-61)
09 Feb 1927
CROOK boundaries redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 48/pp. 57-58)

CURRY

18 Dec 1855
CURRY created by Oregon Territory from COOS and JACKSON. (Ore. Terr. Laws 1855-1856, 7th reg. sess., p. 49)
22 Jan 1856
CURRY lost to creation of JOSEPHINE. (Ore. Terr. Laws 1855-1856, 7th reg. sess., pp. 30-31)
14 Feb 1859
CURRY became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
28 Oct 1872
CURRY lost to COOS. (Ore. Laws 1872, 7th reg. sess., pp. 183-184)
25 Oct 1880
CURRY exchanged with JOSEPHINE. (Ore. Special Laws 1880, 11th reg. sess., p. 93)
09 Feb 1927
CURRY boundary with JOSEPHINE redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 45/pp. 54-55)
30 Apr 1951
CURRY exchanged with COOS when boundary was redefined to run along township and range lines instead of ridge line. (Ore. Laws 1951, 46th reg. sess., ch. 422/pp. 684-687)
08 May 1951
CURRY boundary with COOS clarified to correct an error in the boundary description of 30 April 1951 [no change]. (Ore. Laws 1951, 46th reg. sess., ch. 494/p. 864)
14 Oct 1983
CURRY boundary with COOS redefined to amend description in Oregon Revised Statutes. Became effective 90 days after the end of the legislative session on 16 July [no change]. (Ore. Laws 1983, 62nd reg. sess., ch. 778/pp. 1514-1515)
23 Oct 1999
CURRY boundary with COOS redefined [no change]. (Ore. Laws 1999, 70th reg. sess., ch.600/pp. 1396-1399)

DESCHUTES

01 Feb 1917
DESCHUTES created from CROOK. DESCHUTES creation initially authorized through a vote in the general election of 7 November 1916; Governor's proclamation declared election proceedings valid on 13 December 1916 and creation of DESCHUTES formally approved by the Governor on 1 February 1917. (Ore. Laws 1917, gen., 29th reg. sess., gov. proc./pp. 5-6; ch. 41/pp. 57-61)
09 Feb 1927
DESCHUTES boundaries redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 46/p. 56)

Disputed Area (San Juan Islands, Wash.)

15 Jun 1846
Disputed Area was created when the 1846 treaty between the United States and Great Britain failed to specify which of the multiple passages through the San Juan Islands was meant by "the middle of said channel." Great Britain claimed a line through Rosario Strait, the eastern most passage, while the United States claimed a line through the Strait of Haro, the western most passage. Oregon considered the disputed San Juan Islands to be part of LEWIS (Wash.). The dispute over this water boundary was finally settled on 21 October 1872. (Hayes, 134, 171-174; Parry 100:40-42; Van Zandt, 18)
02 Mar 1853
Disputed Area of the San Juan Islands (Wash.) became a part of Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

DOUGLAS

07 Jan 1852
DOUGLAS created by Oregon Territory from a small part of LANE and from Non-County Area 4. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 18)
22 Dec 1853
DOUGLAS gained from Non-County Area 4; exchanged with LANE. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 13)
28 Jan 1855
Legislature authorized UMPQUA (extinct) to annex a portion of DOUGLAS dependent on a vote in the next general election. The proposed change never took effect. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 20)
18 Dec 1856
DOUGLAS gained Cammas Prairie from COOS. (Ore. Terr. Laws 1856-1857, 8th reg. sess., p. 80)
14 Feb 1859
DOUGLAS became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30)
06 Jul 1863
DOUGLAS gained all of UMPQUA (extinct); exchanged with COOS. Act approved 16 October 1862; became effective 6 July 1863. (Ore. Laws 1862, 2nd reg. sess., p. 59)
21 Oct 1864
DOUGLAS exchanged with COOS. (Ore. Laws 1864, 3rd reg. sess., p. 44)
16 Oct 1868
Legislature authorized the recreation of UMPQUA from DOUGLAS dependent on a vote in an election to be held 3 November 1868, but the re-division of DOUGLAS and UMPQUA never took place. (Ore. Laws 1868, 5th reg. sess., pp. 73-77)
24 Oct 1874
DOUGLAS lost to creation of LAKE. (Ore. Laws 1874, 8th reg. sess., pp. 38-41)
19 Oct 1878
DOUGLAS lost to COOS. (Ore. Special Laws 1878, 10th reg. sess., pp. 162-164)
16 Oct 1882
DOUGLAS exchanged with COOS. (Ore. Special Laws 1882, 12th reg. sess., pp. 83-84)
19 Nov 1885
DOUGLAS lost to LANE. (Ore. Laws 1885, gen., 13th sp. sess., p. 3)
19 Feb 1903
DOUGLAS lost to LANE. (Ore. Laws 1903, 22nd reg. sess., pp. 115-116)
12 Feb 1915
DOUGLAS exchanged with LANE. (Ore. Laws 1915, gen., 28th reg. sess., ch. 65/pp. 74-75)
17 Feb 1915
DOUGLAS exchanged with JACKSON. (Ore. Laws 1915, gen., 28th reg. sess., ch. 116/pp. 114-115)
09 Feb 1927
DOUGLAS exchanged with JOSEPHINE. (Ore. Laws 1927, gen., 34th reg. sess., ch. 45/pp. 54-55)
19 Feb 1927
DOUGLAS south line redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 133/pp. 150-152)
14 Oct 1983
DOUGLAS gained very small area from COOS. Became effective 90 days after the 16 July end of legislative session. (Ore. Laws 1983, 62nd reg. sess., ch. 778/pp. 1514-1515)
23 Oct 1999
DOUGLAS lost small area to COOS when boundary was redefined to run along range line. (Ore. Laws 1999, 70th reg. sess., ch. 600/pp. 1396-1399)

GILLIAM

25 Feb 1885
GILLIAM created from UMATILLA and WASCO. Creation left a small strip of WASCO along the southeastern line of GILLIAM which remained until gained by GILLIAM on 20 February 1891. (Ore. Special Laws 1885, 13th reg. sess., p. 404)
20 Feb 1891
GILLIAM gained from WASCO. The gain was a small strip that was inadvertently separated from WASCO when GILLIAM was created on 25 February 1885. (Ore. Laws 1891, gen., 16th reg. sess., p. 76)
17 Feb 1899
GILLIAM lost to creation of WHEELER and lost a small area along the John Day River to CROOK. (Ore. Laws 1899, 20th reg. sess., pp. 51-55)
09 Feb 1927
GILLIAM redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 52/p. 60)
13 Sep 1967
GILLIAM redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/p. 926)

GRANT

14 Oct 1864
GRANT created from UMATILLA and WASCO. Conflicting boundary definitions in the simultaneous creations of UNION and GRANT created an area of overlap between GRANT and UNION. (Ore. Laws 1864, 3rd reg. sess., p. 43)
20 Oct 1870
GRANT boundaries redefined; lost to BAKER, area of overlap with UNION was reduced. (Ore. Laws 1870, 6th reg. sess., pp. 167-168)
19 Oct 1872
GRANT boundaries redefined; gained from BAKER, area of overlap with UNION increased. (Ore. Laws 1872, 7th reg. sess., pp. 34-35)
24 Oct 1874
GRANT lost to creation of LAKE. (Ore. Laws 1874, 8th reg. sess., pp. 38-41)
16 Oct 1878
GRANT lost to BAKER, lost area of overlap to BAKER and UNION. (Ore. Special Laws 1878, 10th reg. sess., pp. 118-120)
23 Feb 1885
GRANT lost to CROOK. (Ore. Special Laws 1885, 13th reg. sess., pp. 302-303)
21 Nov 1885
GRANT lost to LAKE. (Ore. Laws 1885, gen., 13th sp. sess., p. 6)
25 Feb 1889
GRANT lost to creation of HARNEY. (Ore. Laws 1889, gen., 15th reg. sess., pp. 47-49)
17 Feb 1899
GRANT lost to creation of WHEELER. (Ore. Laws 1899, 20th reg. sess., pp. 51-55)
18 Feb 1905
GRANT redefined [no change]. (Ore. Laws 1905, 23rd reg. sess., ch. 108/pp. 207-208)
27 Jan 1925
GRANT boundaries redefined to run along township and range lines [no mappable change]. (Ore. Laws 1925, gen., 33rd reg. sess., ch. 6/p. 17)

HARNEY

25 Feb 1889
HARNEY created from GRANT. (Ore. Laws 1889, gen., 15th reg. sess., pp. 47-49)
12 Feb 1927
HARNEY gained from MALHEUR when boundary was redefined to run along range lines. (Ore. Laws 1927, gen., 34th reg. sess., ch. 82/pp. 77-78)

HOOD RIVER

23 Jun 1908
HOOD RIVER created from WASCO. HOOD RIVER creation was proposed by initiative petition, approved by a majority of the votes cast at the general election held June 1, 1908 and became effective by Governor's proclamation on June 23 1908. (Ore. Laws 1909, gen., 25th reg. sess., ch. 5/pp. 39-43)
21 Feb 1925
HOOD RIVER boundaries redefined [no change]. (Ore. Laws 1925, gen., 33rd reg. sess., ch. 107/p. 163)
13 Sep 1967
HOOD RIVER redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/p. 927)

ISLAND (Wash.)

22 Dec 1852
ISLAND (Wash.) created by Oregon Territory from THURSTON (Wash.). ISLAND included the disputed San Juan Islands, which were claimed by both the United States and Great Britain from 15 January 1846 to 21 October 1872. (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 46-47)
24 Jan 1853
JEFFERSON (Wash.) attached to ISLAND (Wash.) for judicial purposes. (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 37)
02 Mar 1853
ISLAND (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

JACKSON

12 Jan 1852
JACKSON created by Oregon Territory from Non-County Area 4. (Ore. Terr. Laws 1851, 3rd. reg. sess., pp. 19-20)
22 Dec 1853
JACKSON lost to creation of COOS. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 13)
11 Jan 1854
JACKSON lost to creation of WASCO. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
18 Dec 1855
JACKSON lost to creation of CURRY. (Ore. Terr. Laws 1855-1856, 7th reg. sess., p. 49)
22 Jan 1856
JACKSON lost to creation of JOSEPHINE. (Ore. Terr. Laws 1855-1856, 7th reg. sess., pp. 30-31)
14 Feb 1859
JACKSON became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
01 Oct 1870
Legislature adopted Senate Joint Resolution No. 14 in response to a petition from the citizens of Josephine County asking the legislature to dissolve said county and attach it to Jackson County. Petition for dissolution was referred to the delegation from those two counties in each House. Change never took place. (Ore. Laws 1870, 6th reg. sess., p. 182)
24 Oct 1874
JACKSON lost to creation of LAKE. (Ore. Laws 1874, 8th reg. sess., pp. 38-41)
12 Feb 1885
JACKSON lost to JOSEPHINE. (Ore. Special Laws 1885, 13th reg. sess., pp. 236-237)
17 Feb 1915
JACKSON exchanged with DOUGLAS. (Ore. Laws 1915, gen., 28th reg. sess., ch. 116/pp. 114-115)
09 Feb 1927
JACKSON boundary with JOSEPHINE redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 45/pp. 54-55)

JEFFERSON (Wash.)

22 Dec 1852
JEFFERSON (Wash.) created by Oregon Territory from THURSTON (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 43)
24 Jan 1853
JEFFERSON (Wash.) attached to ISLAND (Wash.) for judicial purposes. (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 37)
01 Feb 1853
JEFFERSON (Wash.) attachment to ISLAND (Wash.) reconfirmed. (Ore. Terr. Laws 1852, 4th reg. sess., p. 52)
02 Mar 1853
JEFFERSON (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

JEFFERSON

12 Dec 1914
JEFFERSON created from CROOK. JEFFERSON creation authorized at the general election of 3 November 1912 and became effective by Governor's proclamation on 12 December 1914. (Ore. Laws 1915, gen., 28th reg. sess., Gov. Proc., pp. 9-10)
09 Feb 1927
JEFFERSON redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 47/pp. 56-57)

JOSEPHINE

22 Jan 1856
JOSEPHINE created by Oregon Territory from CURRY and JACKSON. (Ore. Terr. Laws 1855-1856, 7th reg. sess., pp. 30-31)
14 Feb 1859
JOSEPHINE became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
01 Oct 1870
Legislature adopted Senate Joint Resolution No. 14 in response to a petition from the citizens of Josephine County asking the legislature to dissolve said county and attach it to Jackson County. Petition for dissolution was referred to the delegation from those two counties in each House. Change never took place. (Ore. Laws 1870, 6th reg. sess., p. 182)
25 Oct 1880
JOSEPHINE exchanged with CURRY. (Ore. Special Laws 1880, 11th reg. sess., p. 93)
12 Feb 1885
JOSEPHINE gained from JACKSON. (Ore. Special Laws 1885, 13th reg. sess., pp. 236-237)
09 Feb 1927
JOSEPHINE exchanged with DOUGLAS; boundaries with CURRY and JACKSON redefined. (Ore. Laws 1927, gen., 34th reg. sess., ch. 45/pp. 54-55)

KING (Wash.)

22 Dec 1852
KING (Wash.) created by Oregon Territory from THURSTON (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 41)
24 Jan 1853
KING (Wash.) attached to PIERCE (Wash.) for judicial purposes. (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 37)
01 Feb 1853
KING (Wash.) attachment to PIERCE reconfirmed. (Ore. Terr. Laws 1852, 4th reg. sess., p. 52)
02 Mar 1853
KING (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

KLAMATH

20 Oct 1882
KLAMATH created from LAKE. (Ore. Special Laws 1882, 12th reg. sess., pp. 107-110)
09 Feb 1927
KLAMATH gained from LAKE when boundaries were redefined to run along range lines. (Ore. Laws 1927, gen., 34th reg. sess., ch. 49/p. 58)
19 Feb 1927
KLAMATH redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 136/p. 155)

LAKE

24 Oct 1874
LAKE created from DOUGLAS, GRANT, JACKSON, and WASCO. (Ore. Laws 1874, 8th reg. sess., pp. 38-41)
20 Oct 1882
LAKE lost to creation of KLAMATH. (Ore. Special Laws 1882, 12th reg. sess., pp. 107-110)
21 Nov 1885
LAKE gained from GRANT. (Ore. Laws 1885, gen., 13th sp. sess., p. 6)
09 Feb 1927
LAKE lost to KLAMATH when boundaries were redefined to run along range lines. (Ore. Laws 1927, gen., 34th reg. sess., ch. 49/p. 58)

LANE

28 Jan 1851
LANE created by Oregon Territory from Non-County Area 3 and Non-County Area 4; Non-County Area 3 eliminated. (Ore. Terr. Laws 1850, 2nd sess., pp. 32-33)
07 Jan 1852
LANE lost small area to creation of DOUGLAS. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 18)
22 Dec 1853
LANE gained from UMPQUA (extinct); gained from Non-County Area 4; exchanged with DOUGLAS. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 13)
11 Jan 1854
LANE lost to creation of WASCO. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
14 Feb 1859
LANE became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
19 Nov 1885
LANE gained from DOUGLAS. (Ore. Laws 1885, gen., 13th sp. sess., p. 3)
16 Feb 1887
LANE gained from LINN. (Ore. Laws 1887, gen., 14th reg. sess., p. 126)
19 Feb 1903
LANE gained from DOUGLAS. (Ore. Laws 1903, 22nd reg. sess., pp. 115-116)
29 Jan 1907
LANE exchanged with LINN. (Ore. Laws 1907, gen., 24th reg. sess., ch. 3/pp. 12-14)
19 Feb 1907
LANE gained from LINN. (Ore. Laws 1907, gen., 24th reg. sess., ch. 63/pp. 114-115)
12 Feb 1915
LANE gained from LINN and exchanged with DOUGLAS. Area annexed from LINN was approximately 120 acres along the Willamette River near the present town of Lancaster [too small to map]. (Ore. Laws 1915, gen., 28th reg. sess., ch. 65/pp. 74-77)
15 Feb 1923
LANE lost to BENTON and LINCOLN. (Ore. Laws 1923, gen., 32nd reg. sess., ch. 92/pp. 129-131)
03 Mar 1927
LANE boundary with LINCOLN redefined to correct minor errors in 15 February 1923 description [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 278/pp. 350-351)
06 Mar 1931
LANE gained small area from LINCOLN when boundary was redefined to correct an error in the previous description. (Ore. Laws 1931, gen., 36th reg. sess., ch. 288/p. 514)

LEWIS (Wash.)

21 Dec 1845
LEWIS (Wash.) created by the Provisional Legislature of Oregon Territory from VANCOUVER DISTRICT (now CLARK, Wash.). LEWIS included the San Juan Islands which became a disputed area on 15 June 1846. (Ore. Terr. Laws, general and local, 1843-1849, p. 43)
15 Jun 1846
LEWIS (Wash.) lost to British North America when the Oregon Boundary Treaty between the United States and Great Britain established the northern boundary of Oregon Territory at 49 degrees north latitude. Vague description of the international boundary through Puget Sound resulted in a dispute over the San Juan Islands which the United States considered part of LEWIS. (Hayes, 134, 171-174; Parry 100:40-42; Van Zandt, 18)
03 Feb 1851
LEWIS (Wash.) lost to creation of PACIFIC (Wash.). (Ore. Terr. Laws 1850, 2nd sess., p. 38)
12 Jan 1852
LEWIS (Wash.) lost to creation of THURSTON (Wash.). (Ore. Terr. Laws 1851, 3rd reg. sess., p. 19)
17 Jan 1852
LEWIS (Wash.) exchanged with CLARK (Wash.) when eastern boundary of LEWIS (Wash.) was redefined. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 30)
01 Feb 1853
LEWIS (Wash.) gained from THURSTON (Wash.) and exchanged with CLARK (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40)
02 Mar 1853
LEWIS (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

LINCOLN

20 Feb 1893
LINCOLN created from BENTON and TILLAMOOK. (Ore. Laws 1893, gen., 17th reg. sess., pp. 68-77)
15 Feb 1923
LINCOLN gained from LANE. (Ore. Laws 1923, gen., 32nd reg. sess., ch. 92/pp. 129-131)
03 Mar 1927
LINCOLN gained from BENTON when boundary was redefined to run along range line, and gained from POLK. LINCOLN boundary with LANE redefined to correct minor errors in 15 February 1923 description [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 278/pp. 350-351)
06 Mar 1931
LINCOLN lost small area to LANE when boundary was redefined to correct an error in the previous description. (Ore. Laws 1931, gen., 36th reg. sess., ch. 288/p. 514)
14 Apr 1949
LINCOLN lost to BENTON. (Ore. Laws 1949, gen., 45th reg. sess., ch. 401/pp. 593-596)

LINN

28 Dec 1847
LINN created by the Provisional Legislature of Oregon Territory from CHAMPOEG (now MARION). (Ore. Terr. Laws, general and local, 1843-1849, pp. 55-56)
04 Jan 1851
LINN lost to creation of Non-County Area 3 when the county's southern line redefined. This change apparently made in preparation for creation of LANE on 28 January 1851. (Ore. Terr. Laws 1850, 2nd sess., pp. 33-34)
11 Jan 1854
LINN lost to creation of WASCO. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
17 Jan 1855
LINN south line redefined [no change]. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 34)
14 Feb 1859
LINN became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
16 Feb 1887
LINN lost to LANE. (Ore. Laws 1887, gen., 14th reg. sess., p. 126)
29 Jan 1907
LINN exchanged with LANE. (Ore. Laws 1907, gen., 24th reg. sess., ch. 3/pp. 12-14)
19 Feb 1907
LINN lost to LANE. (Ore. Laws 1907, gen., 24th reg. sess., ch. 63/pp. 114-115)
25 Feb 1913
LINN gained from MARION. (Ore. Laws 1913, gen., 27th reg. sess., ch. 109/p. 184)
12 Feb 1915
LINN lost to LANE. Area annexed from LINN was approximately 120 acres along the Willamette River near the present town of Lancaster [too small to map]. (Ore. Laws 1915, gen., 28th reg. sess., ch. 65/pp. 76-77)
23 May 1985
LINN boundary with MARION redefined to run along the middle of the main channel of the Santiam River, and along the middle of the main channel of the north fork of the Santiam River as they existed on 21 April 1982 [no mappable change]. (Ore. Laws 1985, 63rd reg. sess., ch. 122/p. 407)

MALHEUR

01 Apr 1887
MALHEUR created from BAKER. (Ore. Laws 1887, gen., 14th reg. sess., pp. 138-141)
12 Feb 1927
MALHEUR lost to HARNEY when boundary was redefined to run along range lines. (Ore. Laws 1927, gen., 34th reg. sess., ch. 82/pp. 77-78)
06 Feb 1931
MALHEUR exchanged with BAKER. (Ore. Laws 1931, gen., 36th reg. sess., ch. 18/pp. 26-28)

MARION

05 Jul 1843
CHAMPOEG DISTRICT (now MARION) created. CHAMPOEG was one of four original counties created by the Provisional Legislature of Oregon Territory. Included parts of present Oregon, Washington, Idaho, and Montana. Name was also spelled CHAMPOOICK. (Oregon Archives, p. 26)
19 Dec 1845
CHAMPOEG DISTRICT (now MARION) lost to CLACKAMAS DISTRICT. Boundary between CHAMPOEG DISTRICT and YAMHILL DISTRICT redefined to run "along the middle of the main channel of the Willamette River to the center of the Columbia River at the upper mouth of the Willamette." (Ore. Terr. Laws, general and local, 1843-1849, pp. 35-37)
22 Dec 1845
CHAMPOEG DISTRICT (now MARION) renamed CHAMPOEG County; no change in boundaries [not mapped]. (Ore. Terr. Laws, general and local, 1843-1849, p.35)
28 Dec 1847
CHAMPOEG (now MARION) lost to creation of LINN. (Ore. Terr. Laws, general and local, 1843-1849, pp. 55-56)
03 Sep 1849
CHAMPOEG renamed MARION. (Ore. Terr. Laws 1850, 2nd sess., p. 53)
11 Jan 1854
MARION lost to creation of WASCO. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
30 Jan 1856
MARION lost to CLACKAMAS. (Ore. Terr. Laws 1855-1856, 7th reg. sess., p. 50)
14 Feb 1859
MARION became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
08 Feb 1911
MARION boundary with CLACKAMAS redefined [no change]. (Ore. Laws 1911, gen., 26th reg. sess., ch. 22/p. 39)
25 Feb 1913
MARION lost to LINN. (Ore. Laws 1913, gen., 27th reg. sess., ch. 109/p. 184)
22 Jun 1981
MARION boundary with YAMHILL redefined to run along middle of the main channel of the Willamette River as it was located on 22 June 1981 [no mappable change]. (Ore. Laws 1981, 61st reg. sess., ch. 214/p. 225)
05 Aug 1983
MARION boundary with POLK redefined to run along main channel of Willamette River as it was located on 22 June 1981 [no mappable change]. (Ore. Laws 1983, 62nd reg. sess., ch. 780/pp. 1516-1517)
23 May 1985
MARION boundary with LINN redefined to run along the middle of the main channel of the Santiam River, and along the middle of the main channel of the north fork of the Santiam River as they existed on 21 April 1982 [no mappable change]. (Ore. Laws 1985, 63rd reg. sess., ch. 122/p. 407)

MORROW

16 Feb 1885
MORROW created from UMATILLA and WASCO. (Ore. Special Laws 1885, 13th reg. sess., pp. 239-243)
13 Sep 1967
MORROW redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/p. 927)

MULTNOMAH

22 Dec 1854
MULTNOMAH created by Oregon Territory from CLACKAMAS and WASHINGTON. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 29)
14 Jan 1857
MULTNOMAH lost very small area near the head of Eagle Creek and Bradford's Island to WASCO [change too small to map]. (Ore. Terr. Laws 1856-1857, 8th reg. sess., pp. 78-79)
14 Feb 1859
MULTNOMAH became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
24 Oct 1864
MULTNOMAH gained from COLUMBIA. (Ore. Laws 1864, 3rd reg. sess., p. 62)
24 Feb 1885
MULTNOMAH gained from COLUMBIA. (Ore. Special Laws 1885, 13th reg. sess., p. 324)
20 Feb 1893
MULTNOMAH gained small area (part of the town of Sellwood) from CLACKAMAS. (Ore. Laws 1893, gen., 17th reg. sess., pp. 78-79)
25 Feb 1895
MULTNOMAH boundary with WASCO adjusted within Section 22 of Township 2 North, Range 7 East [change too small to map]. (Ore. Laws 1895, 18th reg. sess., p. 88)
25 Feb 1901
MULTNOMAH exchanged with COLUMBIA. (Ore. Laws 1901, 21st reg. sess., pp. 126-127)
06 Mar 1931
MULTNOMAH lost to COLUMBIA. (Ore. Laws 1931, gen., 36th reg. sess., ch. 289/p. 515)
13 Sep 1967
MULTNOMAH redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/p. 928)

Non-County Area 1

27 Jun 1844
Non-County Area 1 created by the Provisional Legislature of Oregon Territory from parts of TUALITY DISTRICT (now WASHINGTON) and CLACKAMAS DISTRICT when the county lines were redefined to run along the Columbia River. Non-County Area 1 became VANCOUVER DISTRICT (later CLARK, Wash.) on 20 August 1845. (Ore. Terr. Laws, general and local, 1843-1849, p. 74)
20 Aug 1845
Non-County Area 1 lost all territory to creation of VANCOUVER DISTRICT (now CLARK, Wash.); Non-County Area 1 eliminated. (Ore. Terr. Laws 1845, p. 22)

Non-County Area 2

19 Dec 1845
Non-County Area 2 created by the Provisional Legislature of Oregon Territory from YAMHILL DISTRICT when the district's boundaries redefined. This change apparently made in preparation for the 22 December 1845 creation of POLK. (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
22 Dec 1845
Non-County Area 2 lost to creation of POLK; Non-County Area 2 eliminated. (Ore. Terr. Laws, general and local, 1843-1849, p. 38)

Non-County Area 3

04 Jan 1851
Non-County Area 3 created by Oregon Territory from LINN when the county's southern boundary redefined. This change apparently made in preparation for creation of LANE on 28 January 1851. (Ore. Terr. Laws 1850, 2nd sess., pp. 33-34)
28 Jan 1851
Non-County Area 3 lost to creation of LANE; Non-County Area 3 eliminated. (Ore. Terr. Laws 1850, 2nd sess., pp. 32-33)

Non-County Area 4

15 Jan 1851
Non-County Area 4 created by Oregon Territory from BENTON when the county’s southern boundary redefined. This change apparently made in preparation for creation of UMPQUA (extinct) on 24 January 1851, and creation of LANE on 28 January 1851. (Ore. Terr. Laws 1850, 2nd sess., p. 34)
24 Jan 1851
Non-County Area 4 lost to creation of UMPQUA (extinct); remainder of Non-County Area 4 attached to UMPQUA "for civil and military purposes." (Ore. Terr. Laws 1850, 2nd sess., p. 33)
28 Jan 1851
Non-County Area 4 lost to creation of LANE. (Ore. Terr. Laws 1850, 2nd sess., pp. 32-33)
07 Jan 1852
Non-County Area 4 lost to creation of DOUGLAS. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 18)
12 Jan 1852
Non-County Area 4 lost to creation of JACKSON. (Ore. Terr. Laws 1851, 3rd. reg. sess., pp. 19-20)
22 Dec 1853
Non-County Area 4 lost to DOUGLAS and LANE; Non-County Area 4 eliminated. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 13)

Overlap Area

14 Oct 1864
Area of overlap created by conflicting boundary definitions in the simultaneous creations of GRANT and UNION. (Ore. Laws 1864, 3rd reg. sess., pp. 37, 43)
20 Oct 1870
Area of overlap between GRANT and UNION was reduced when GRANT boundaries were redefined. (Ore. Laws 1870, 6th reg. sess., pp. 167-168)
19 Oct 1872
Area of overlap between GRANT and UNION was enlarged when GRANT boundaries were redefined. (Ore. Laws 1872, 7th reg. sess., pp. 34-35)
16 Oct 1878
Area of overlap between GRANT and UNION was divided between BAKER and UNION; overlap area eliminated. (Ore. Special Laws 1878, 10th reg. sess., pp. 118-120)

PACIFIC (Wash.)

03 Feb 1851
PACIFIC (Wash.) created by Oregon Territory from LEWIS (Wash.); PACIFIC not fully organized, attached to CLATSOP "for all judicial purposes." (Ore. Terr. Laws 1850, 2nd sess., p. 38)
28 Jan 1852
PACIFIC (Wash.) fully organized, detached from CLATSOP. (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40)
02 Mar 1853
PACIFIC (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

PIERCE (Wash.)

22 Dec 1852
PIERCE (Wash.) created by Oregon Territory from THURSTON (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 44-45)
24 Jan 1853
KING (Wash.) attached to PIERCE (Wash.) for judicial purposes. (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 37)
02 Mar 1853
PIERCE (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

POLK

22 Dec 1845
POLK created by the Provisional Legislature of Oregon Territory from Non-County Area 2; Non-County Area 2 eliminated. (Ore. Terr. Laws, general and local, 1843-1849, p. 38)
23 Dec 1847
POLK lost to creation of BENTON. On 20 December 1847 the Journal of the Provisional Legislature recorded the passage of an act to redefine the boundaries of POLK. No such act appears within the session laws, but the definition of BENTON depends on an earlier change having been made to the south line of POLK. (Ore. Terr. Laws, general and local, 1843-1849, p. 50; Holman, 28-30; Oregon Archives, 237)
15 Dec 1853
POLK lost to creation of TILLAMOOK. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 6)
14 Feb 1859
POLK became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
21 Feb 1891
POLK exchanged with TILLAMOOK. (Ore. Laws 1891, gen., 16th reg. sess., pp. 139-140)
03 Mar 1927
POLK lost small corner to LINCOLN. (Ore. Laws 1927, gen., 34th reg. sess., ch. 278/pp. 350-351)
13 Jul 1981
POLK redefined to amend description in Oregon Revised Statutes [no change]. (Ore. Laws 1981, 61st reg. sess., ch. 332/p. 356)
05 Aug 1983
POLK boundary redefined to run along main channel of Willamette River as it was located on 22 June 1981 [no mappable change]. (Ore. Laws 1983, 62nd reg. sess., ch. 780/pp. 1516-1517)

SHERMAN

25 Feb 1889
SHERMAN created from WASCO. (Ore. Laws 1889, gen., 15th reg. sess., p. 82)
19 Feb 1891
SHERMAN gained from WASCO. (Ore. Laws 1891, gen., 16th reg. sess., pp. 68-69)
09 Feb 1927
SHERMAN redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 53/pp. 60-61)
13 Sep 1967
SHERMAN redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/pp. 928-929)

THURSTON (Wash.)

12 Jan 1852
THURSTON (Wash.) created by Oregon Territory from CLARK (Wash.) and LEWIS (Wash.). THURSTON included the disputed San Juan Islands which were claimed by both the United States and Great Britain from 15 January 1846 to 21 October 1872. (Ore. Terr. Laws 1851, 3rd reg. sess., p. 19)
22 Dec 1852
THURSTON (Wash.) lost to creation of ISLAND (Wash.), JEFFERSON (Wash.), KING (Wash.) and PIERCE (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 41-47)
01 Feb 1853
THURSTON (Wash.) lost to LEWIS (Wash.). (Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40)
02 Mar 1853
THURSTON (Wash.) became a county in Washington Territory; eliminated from Oregon Territory. (U.S. Stat., vol. 10. ch. 90[1853]/pp. 172-173; Van Zandt, 155)

TILLAMOOK

15 Dec 1853
TILLAMOOK created by Oregon Territory from CLATSOP, POLK, and YAMHILL; TILLAMOOK not fully organized, attached to YAMHILL "for judicial purposes." (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 6; Ore. Terr. Rev. Stat. 1853, p. 63)
15 Jan 1855
TILLAMOOK lost to CLATSOP. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 33)
14 Feb 1859
TILLAMOOK became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
22 Oct 1870
TILLAMOOK gained from CLATSOP; attached to YAMHILL "for judicial purposes." (Ore. Laws 1870, 6th reg. sess., pp. 24-25)
15 Feb 1887
TILLAMOOK exchanged with YAMHILL. (Ore. Laws 1887, gen., 14th reg. sess., p. 147)
20 Feb 1891
TILLAMOOK gained from CLATSOP. (Ore. Laws 1891, gen., 16th reg. sess., pp. 102-103)
21 Feb 1891
TILLAMOOK exchanged with POLK. (Ore. Laws 1891, gen., 16th reg. sess., pp. 139-140)
20 Feb 1893
TILLAMOOK lost to creation of LINCOLN, and lost to CLATSOP. (Ore. Laws 1893, gen., 17th reg. sess., pp. 68-78)
22 Feb 1893
TILLAMOOK exchanged with WASHINGTON. (Ore. Laws 1893, gen., 17th reg. sess., pp. 161-162)
13 Jul 1981
TILLAMOOK redefined to amend description in Oregon Revised Statutes [no change]. (Ore. Laws 1981, 61st reg. sess., ch. 332/pp. 355-356)

TUALITY (see WASHINGTON)

UMATILLA

27 Sep 1862
UMATILLA created from WASCO. (Ore. Laws 1862, 2nd reg. sess., p. 91)
14 Oct 1864
UMATILLA lost to creation of GRANT. (Ore. Laws 1864, 3rd reg. sess., p. 43)
16 Feb 1885
UMATILLA lost to creation of MORROW. Creation resulted in UMATILLA being divided into two parts encompassing territory both east and west of MORROW. Division remained until 25 February 1885 when creation of GILLIAM eliminated the western portion. (Ore. Special Laws 1885, 13th reg. sess., pp. 239-243)
25 Feb 1885
UMATILLA lost to creation of GILLIAM. (Ore. Special Laws 1885, 13th reg. sess., p. 404)
13 Feb 1907
UMATILLA exchanged with UNION, lost to WALLOWA. Two mistakes in the line as described were corrected on 27 February 1913. (Ore. Laws 1907, gen., 24th reg. sess., ch. 20/pp. 29-31)
27 Feb 1913
UMATILLA boundary with UNION and WALLOWA redefined to correct two mistakes in the boundary description of 13 February 1907 [no change to line as previously drawn]. (Ore. Laws 1913, gen., 27th reg. sess., ch. 309/pp. 598-600)
13 Sep 1967
UMATILLA redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/pp. 929-930)

UMPQUA (extinct)

24 Jan 1851
UMPQUA (extinct) created by Oregon Territory from part of Non-County Area 4; remainder of Non-County Area 4 attached to UMPQUA "for civil and military purposes." (Ore. Terr. Laws 1850, 2nd sess., p. 33)
22 Dec 1853
UMPQUA (extinct) lost to creation of COOS; lost to LANE. COOS not fully organized, attached to UMPQUA "for judicial purposes." (Ore. Terr. Special Laws 1853, 5th reg. sess., p. 13; Ore. Terr. Rev. Stat. 1853, p. 63)
28 Jan 1855
Legislature authorized UMPQUA (extinct) to annex a portion of DOUGLAS dependent on a vote in the next general election. The proposed change never took effect. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 20)
14 Feb 1859
UMPQUA (extinct) became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
06 Jul 1863
UMPQUA (extinct) lost all territory to DOUGLAS in "an act to consolidate the counties of Douglas and Umpqua into one county under the name of Douglas"; UMPQUA eliminated. Act approved 16 October 1862; became effective 6 July 1863. (Ore. Laws 1862, 2nd reg. sess., p. 59)

UMPQUA (proposed)

16 Oct 1868
Legislature authorized the recreation of UMPQUA from DOUGLAS dependent on a vote in an election to be held 3 November 1868, but the re-division of UMPQUA and DOUGLAS never took place. (Ore. Laws 1868, 5th reg. sess., pp. 73-77)

UNION

14 Oct 1864
UNION created from BAKER. Conflicting boundary definitions in the simultaneous creations of UNION and GRANT created an area of overlap between GRANT and UNION. (Ore. Laws 1864, 3rd reg. sess., p. 37)
20 Oct 1870
Area of overlap between UNION and GRANT was reduced when GRANT boundaries were redefined. (Ore. Laws 1870, 6th reg. sess., pp. 167-168)
19 Oct 1872
Area of overlap between UNION and GRANT was increased when GRANT boundaries were redefined. (Ore. Laws 1872, 7th reg. sess., pp. 34-35)
26 Oct 1874
In an effort to resolve boundary conflicts between BAKER, GRANT, and UNION the legislature passed "An Act to Create a Commission from Grant and Baker Counties, to establish an Initial Point to define the Boundary Line between Grant and Baker Counties, and to Create a Commission from Baker and Union Counties to designate by Name which Fork of the North Fork of Powder River shall be the line between Baker and Union Counties." (Ore. Laws 1874, 8th reg. sess., pp. 91-92)
16 Oct 1878
UNION gained area of overlap from GRANT, lost to BAKER. (Ore. Special Laws 1878, 10th reg. sess., pp. 118-120)
11 Feb 1887
UNION lost to creation of WALLOWA. (Ore. Laws 1887, gen., 14th reg. sess., pp. 142-145)
18 Feb 1899
UNION lost to WALLOWA. (Ore. Laws 1899, 20th reg. sess., p. 169)
01 Mar 1901
UNION lost to BAKER. (Ore. Laws 1901, 21st reg. sess., pp. 435-438)
13 Feb 1907
UNION exchanged with UMATILLA. Two mistakes in the line as described were corrected on 27 February 1913. (Ore. Laws 1907, gen., 24th reg. sess., ch. 20/pp. 29-31)
27 Feb 1913
UNION boundary WALLOWA redefined to correct two mistakes in the boundary description of 13 February 1907 [no change to line as previously drawn]. (Ore. Laws 1913, gen., 27th reg. sess., ch. 309/pp. 598-600)
23 Feb 1915
UNION exchanged with WALLOWA. (Ore. Laws 1915, gen., 28th reg. sess., ch. 134/pp. 145-146)

VANCOUVER (Wash.) (see CLARK, Wash.)

WALLOWA

11 Feb 1887
WALLOWA created from UNION. (Ore. Laws 1887, gen., 14th reg. sess., pp. 142-145)
18 Feb 1899
WALLOWA gained from UNION. (Ore. Laws 1899, 20th reg. sess., p. 169)
13 Feb 1907
WALLOWA gained from UMATILLA. Two mistakes in the line as described were corrected on 27 February 1913. (Ore. Laws 1907, gen., 24th reg. sess., ch. 20/pp. 29-31)
27 Feb 1913
WALLOWA boundary with UMATILLA and UNION redefined to correct two mistakes in the boundary description of 13 February 1907 [no change to line as previously drawn]. (Ore. Laws 1913, gen., 27th reg. sess., ch. 309/pp. 598-600)
23 Feb 1915
WALLOWA lost to BAKER, exchanged with UNION. (Ore. Laws 1915, gen., 28th reg. sess., ch. 134/pp. 145-146)

WASCO

11 Jan 1854
WASCO created by Oregon Territory from CLACKAMAS, JACKSON, LANE, LINN, and MARION. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 26-27)
14 Jan 1857
WASCO gained very small area near the head of Eagle Creek and Bradford's Island from MULTNOMAH [change too small to map]. (Ore. Terr. Laws 1856-1857, 8th reg. sess., pp. 78-79)
14 Feb 1859
WASCO lost to Washington Territory when the United States created the state of Oregon from Oregon Territory. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
22 Sep 1862
WASCO lost to creation of BAKER. (Ore. Laws 1862, 2nd reg. sess., p. 112)
27 Sep 1862
WASCO lost to creation of UMATILLA. (Ore. Laws 1862, 2nd reg. sess., p. 91)
14 Oct 1864
WASCO lost to creation of GRANT. (Ore. Laws 1864, 3rd reg. sess., p. 43)
24 Oct 1874
WASCO lost to creation of LAKE. (Ore. Laws 1874, 8th reg. sess., pp. 38-41)
24 Oct 1882
WASCO lost to creation of CROOK. (Ore. Special Laws 1882, 12th reg. sess., p. 178)
16 Feb 1885
WASCO lost to creation of MORROW. (Ore. Special Laws 1885, 13th reg. sess., pp. 239-243)
25 Feb 1885
WASCO lost to creation of GILLIAM. Creation left a small strip of WASCO along the southeastern line of GILLIAM which remained until gained by GILLIAM on 20 February 1891. (Ore. Special Laws 1885, 13th reg. sess., p. 404)
25 Feb 1889
WASCO lost to creation of SHERMAN. (Ore. Laws 1889, gen., 15th reg. sess., p. 82)
19 Feb 1891
WASCO lost to SHERMAN. (Ore. Laws 1891, gen., 16th reg. sess., pp. 68-69)
20 Feb 1891
WASCO lost to GILLIAM. The gain was a small strip that was inadvertently separated from WASCO when GILLIAM was created on 25 February 1885. (Ore. Laws 1891, gen., 16th reg. sess., p. 76)
25 Feb 1895
WASCO boundary with MULTNOMAH adjusted within Section 22 of Township 2 North, Range 7 East [change too small to map]. (Ore. Laws 1895, 18th reg. sess., p. 88)
23 Jun 1908
WASCO lost to creation of HOOD RIVER. (Ore. Laws 1909, gen., 25th reg. sess., ch. 5/pp. 39-43)
25 Feb 1925
WASCO boundaries redefined [no change]. (Ore. Laws 1925, gen., 33rd reg. sess., ch. 108/p. 164)
13 Sep 1967
WASCO redefined to substitute "boundary of the state" for middle of the main channel of the Columbia River. Approved by the Governor 19 June 1967, became effective 13 Sep 1967 [no change]. (Ore. Laws 1967, 54th reg. sess., ch. 421/pp. 930-931)

WASHINGTON

05 Jul 1843
TUALITY DISTRICT (now WASHINGTON) created. TUALITY was one of four original counties created by the Provisional Legislature of Oregon Territory. Included parts of present Oregon, Washington, and Canada. County was also variously identified as TWALITY, TUALITZ, and FALATINE. (Oregon Archives, p. 26)
22 Jun 1844
Provisional Legislature of Oregon Territory authorized the creation of CLATSOP, presumably from the northern and western portions of TUALITY DISTRICT (now WASHINGTON). Introduction and passage of the bill creating CLATSOP appears only within the session minutes for the Journal of the Provisional Legislature (1844), and no act regarding its creation appears in the general or special laws. No boundary description for the new county is given. See 19 December 1845 for the first mappable description of CLATSOP from TUALITY. (Holman, p. 25; Oregon Archives, p. 43)
26 Jun 1844
TUALITY DISTRICT (now WASHINGTON) lost to YAMHILL DISTRICT. (Ore. Terr. Laws, general and local, 1843-1849, p. 87)
27 Jun 1844
TUALITY DISTRICT (now WASHINGTON) lost to creation of Non-County Area 1 when the TUALITY boundary was redefined to run along the Columbia River. (Ore. Terr. Laws, general and local, 1843-1849, p. 74)
19 Dec 1845
TUALITY DISTRICT (now WASHINGTON) gained from YAMHILL DISTRICT and lost to CLATSOP when CLATSOP was defined for the first time. Boundary between TUALITY DISTRICT and CLACKAMAS DISTRICT redefined to run "along the middle of the main channel of the Willamette River to the center of the Columbia River at the upper mouth of the Willamette". (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
22 Dec 1845
TUALITY DISTRICT (now WASHINGTON) renamed TUALITY County; no change in boundaries [not mapped]. (Ore. Terr. Laws, general and local, 1843-1849, p. 35)
11 Dec 1846
TUALITY (now WASHINGTON) lost to YAMHILL. (Ore. Terr. Laws, general and local, 1843-1849, p. 7)
03 Sep 1849
TUALITY renamed WASHINGTON. (Ore. Terr. Laws 1850, 2nd sess., p. 54)
16 Jan 1854
WASHINGTON lost to creation of COLUMBIA. (Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 32-33)
22 Dec 1854
WASHINGTON lost to creation of MULTNOMAH, and lost to CLACKAMAS. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 29)
15 Jan 1855
WASHINGTON gained from CLATSOP when CLATSOP was redefined. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 33)
30 Jan 1855
WASHINGTON exchanged with YAMHILL when YAMHILL boundaries were redefined. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 46)
21 Jan 1856
WASHINGTON exchanged with YAMHILL when YAMHILL boundaries were redefined. (Ore. Terr. Laws 1855-1856, 7th reg. sess., pp. 40-41)
22 Jan 1857
WASHINGTON exchanged with YAMHILL. (Ore. Terr. Laws 1856-1857, 8th reg. sess., p. 15)
14 Feb 1859
WASHINGTON became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
17 Oct 1862
WASHINGTON lost to CLACKAMAS. (Ore. Laws 1862, 2nd reg. sess., p. 98)
24 Feb 1885
WASHINGTON exchanged with COLUMBIA. (Ore. Special Laws 1885, 13th reg. sess., p. 324)
22 Feb 1893
WASHINGTON exchanged with CLACKAMAS, TILLAMOOK, and YAMHILL. (Ore. Laws 1893, gen., 17th reg. sess., pp. 161-162)
15 Oct 1898
WASHINGTON gained from COLUMBIA. (Ore. Laws 1898, 20th spec. sess., pp. 27-28)
25 Feb 1901
WASHINGTON lost to COLUMBIA. (Ore. Laws 1901, 21st reg. sess., pp. 126-127)
21 Feb 1903
WASHINGTON gained from COLUMBIA. (Ore. Laws 1903, 22nd reg. sess., pp. 151-152)

WHEELER

17 Feb 1899
WHEELER created from CROOK, GILLIAM, and GRANT. (Ore. Laws 1899, 20th reg. sess., pp. 51-55)
27 Feb 1901
WHEELER gained small area along the John Day River from CROOK. (Ore. Laws 1901, 21st reg. sess., pp. 291-292)
12 Feb 1927
WHEELER redefined [no change]. (Ore. Laws 1927, gen., 34th reg. sess., ch. 70/p. 71)

YAMHILL

05 Jul 1843
YAMHILL DISTRICT created. YAMHILL was one of four original counties created by the Provisional Legislature of Oregon Territory. (Oregon Archives, p. 26)
26 Jun 1844
YAMHILL DISTRICT gained from TUALITY DISTRICT (now WASHINGTON). (Ore. Terr. Laws, general and local, 1843-1849, p. 87)
19 Dec 1845
YAMHILL DISTRICT lost to TUALITY DISTRICT (now WASHINGTON); lost to creation of Non-County Area 2, apparently in preparation for the 22 December 1845 creation of POLK. Boundary between YAMHILL DISTRICT and CHAMPOEG DISTRICT (now MARION) redefined to run "along the middle of the main channel of the Willamette River to the center of the Columbia River at the upper mouth of the Willamette." (Ore. Terr. Laws, general and local, 1843-1849, pp. 36-37)
22 Dec 1845
YAMHILL DISTRICT renamed YAMHILL County; no change in boundaries [not mapped]. (Ore. Terr. Laws, general and local, 1843-1849, p. 35)
11 Dec 1846
YAMHILL gained from CLATSOP and TUALITY (now WASHINGTON). (Ore. Terr. Laws, general and local, 1843-1849, p. 7)
15 Dec 1853
YAMHILL lost to creation of TILLAMOOK. (Ore. Terr. Special Laws, 1853, 5th reg. sess., p. 6)
22 Dec 1853
TILLAMOOK attached to YAMHILL "for judicial purposes." (Ore. Terr. Rev. Stat. 1853, p. 63)
22 Dec 1854
YAMHILL lost small area to CLACKAMAS. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 29)
30 Jan 1855
YAMHILL boundaries redefined; exchanged with WASHINGTON. (Ore. Terr. Special Laws 1854, 6th reg. sess., p. 46)
21 Jan 1856
YAMHILL boundaries redefined; exchanged with WASHINGTON. (Ore. Terr. Laws 1855-1856, 7th reg. sess., pp. 40-41)
22 Jan 1857
YAMHILL exchanged with WASHINGTON. (Ore. Terr. Laws 1856-1857, 8th reg. sess., p. 15)
14 Feb 1859
YAMHILL became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. (U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384 Ore. Laws 1860, 1st reg. sess., pp. 28-30)
17 Oct 1860
YAMHILL lost to CLACKAMAS. (Ore. Laws 1860, 1st reg. sess., p. 47)
22 Oct 1870
TILLAMOOK attached to YAMHILL "for judicial purposes." (Ore. Laws 1870, 6th reg. sess., pp. 24-25)
15 Feb 1887
YAMHILL exchanged with TILLAMOOK. (Ore. Laws 1887, gen., 14th reg. sess., p. 147)
22 Feb 1893
YAMHILL exchanged with WASHINGTON. (Ore. Laws 1893, gen., 17th reg. sess., pp. 161-162)
22 Jun 1981
YAMHILL boundary with MARION redefined to run along middle of the main channel of the Willamette River as it was located on 22 June 1981 [no mappable change]. (Ore. Laws 1981, 61st reg. sess., ch. 214/p. 225)
13 Jul 1981
YAMHILL redefined to amend description in Oregon Revised Statutes [no change]. (Ore. Laws 1981, 61st reg. sess., ch. 332/p. 356)