Arizona: Individual County Chronologies

Arizona 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

APACHE

14 Feb 1879
APACHE created by Arizona Territory from YAVAPAI. (Ariz. Terr. Laws 1879, 10th assy./ pp. 96-97)
10 Mar 1881
APACHE lost to creation of GRAHAM. (Ariz. Terr. Laws 1881, 11th assy./ pp. 155-157)
21 Mar 1895
APACHE lost to creation of NAVAJO. (Ariz. Terr. Laws 1895, 18th assy./ pp. 96-105)
17 Mar 1897
Boundary between APACHE and GRAHAM clarified [no change]. (Ariz. Terr. Laws 1897, 19th assy./ p. 67)

ARIZONA (N.M. Territory, extinct)

01 Feb 1860
ARIZONA (N.M. Territory, extinct) created by New Mexico Territory from DOŅA ANA (N.M.). ARIZONA (extinct) was located entirely within present Arizona. (N.M. Terr. Laws 1859-1860, 9th assy. /p. 74)
18 Jan 1862
ARIZONA (N.M. Territory, extinct) eliminated when it lost all territory to DOŅA ANA. (N.M.). (N.M. Terr. Laws 1861-1862, 11th assy. /p. 18)
28 Jan 1863
ARIZONA (N.M. Territory, extinct) re-created from DOŅA ANA (N.M.). (N.M. Terr. Laws 1862-1863, 12th assy. /p.30)
24 Feb 1863
ARIZONA (N.M. Territory, extinct) eliminated when Arizona Territory was created from New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

Arizona Territory (non-county area)

24 Feb 1863
Arizona Territory created by the United States from the western portion of New Mexico Territory and a part of present Nevada. Arizona did not immediately create any counties. BERNALILLO (N.M.), DOŅA ANA (N.M.), RIO ARRIBA (N.M.), SANTA ANA (N.M. Territory, extinct), SOCORRO (N.M.), TAOS (N.M.) and VALENCIA (N.M.) all eliminated from Arizona Territory, ARIZONA (N.M. Territory, extinct) eliminated entirely. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)
05 May 1866
Arizona Territory lost parts of MOHAVE and PAH-UTE (extinct) when the United States transferred the portion of Arizona Territory lying between 37 degrees and 42 degrees of north latitude and west of 114 degrees west longitude to the state of Nevada. Arizona twice petitioned Congress (5 May 1866 and 5 October 1867) to repeal the act of transfer and did not officially recognize the loss until 18 February 1871 when a change to the boundaries of MOHAVE implicitly acknowledged the new Arizona - Nevada line. (U.S. Stat., vol. 14, ch. 73[1866]/p. 43; Van Zandt, 158, 165; Ariz. Terr. Laws 1867, 3rd assy./ pp. 67-68; Ariz. Terr. Laws 1868, 4th assy./ pp. 68-69)

BERNALILLO (N.M.)

22 Sep 1846
BERNALILLO (N.M.) established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852
BERNALILLO (N.M.) gained from VALENCIA (N.M.) and non-county area, exchanged with SAN MIGUEL (N.M.), and lost to SANTA ANA (N.M.) and SANTA FE (N.M.) when all counties redefined; included parts of present Arizona, Nevada and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 292)
24 Feb 1863
BERNALILLO (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

CASTLE DOME (proposed)

05 Apr 1860
An unofficial convention held in Tucson established a provisional government, declared the creation of the Territory of Arizona from all that part of New Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and authorized the creation of CASTLE DOME (proposed). Congress failed to recognize the new territory and its proposed counties [no change]. (Sacks, 36, 151; Swindler, 1:244-248)

COCHISE

01 Feb 1881
COCHISE created by Arizona Territory from PIMA. (Ariz. Terr. Laws 1881, 11th assy./ pp. 4-7)
11 Feb 1935
COCHISE boundaries redefined [no change]. (Ariz. Laws 1935, 12th reg. sess., ch. 7/p. 11)
14 Mar 1968
COCHISE gained from SANTA CRUZ when the boundary was redefined to run along the east line of range 18 east. (Ariz. Laws 1968, 28th leg., 1st reg. sess., ch. 82/ pp. 180-182)

COCONINO

19 Feb 1891
COCONINO created by Arizona Territory from YAVAPAI. (Ariz. Terr. Laws 1891, 16th assy./ pp. 26-34)

Disputed Area

13 Dec 1850
Faulty geographic information on the Disturnell map referenced in the Treaty of Guadalupe-Hidalgo led to a dispute between the United States and Mexico over the exact location and extent of the international boundary. Map shows only the part of Disputed Area in present Arizona. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
09 Jan 1852
Dispute between the United States and Mexico over the exact location and extent of the international boundary continued. Map shows the entire Disputed Area. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
30 Dec 1853
Gadsden Purchase settled the boundary dispute between the United States and Mexico and established the international line at its present location; Disputed Area eliminated. (U.S. Stat., vol. 10, pp. 1031-1037; Van Zandt, 11, 29, 162)

DOŅA ANA (N.M.)

09 Jan 1852
DOŅA ANA (N.M.) created by New Mexico Territory from non-county area; included parts of present Arizona and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 1st sess./p. 119; N.M. Terr. Laws 1851, 1st assy., 2d sess. /pp. 266, 292)
03 Feb 1855
DOŅA ANA (N.M.) gained all of non-county area (Gadsden Purchase) in New Mexico Territory; non-county area eliminated. (N.M. Terr. Laws 1854, 4th assy. /p. 57)
01 Feb 1860
DOŅA ANA (N.M.) lost to creation of ARIZONA (N.M. Territory, extinct). (N.M. Terr. Laws 1859-1860, 9th assy. /p. 74)
18 Jan 1862
DOŅA ANA (N.M.) gained all of ARIZONA (N.M. Territory, extinct); ARIZONA eliminated. (N.M. Terr. Laws 1861-1862, 11th assy. /p. 18)
28 Jan 1863
DOŅA ANA (N.M.) lost to re-creation of ARIZONA (N.M. Territory, extinct). (N.M. Terr. Laws 1862-1863, 12th assy. /p.30)
24 Feb 1863
DOŅA ANA (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

DOŅA ANA (proposed)

05 Apr 1860
An unofficial convention held in Tucson established a provisional government, declared the creation of the Territory of Arizona from all that part of New Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and authorized the creation of DOŅA ANA (proposed). Congress failed to recognize the new territory and its proposed counties [no change]. (Sacks, 36, 151; Swindler, 1:244-248)

EWELL (proposed)

05 Apr 1860
An unofficial convention held in Tucson established a provisional government, declared the creation of the Territory of Arizona from all that part of New Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and authorized the creation of EWELL (proposed). Congress failed to recognize the new territory and its proposed counties [no change]. (Sacks, 36, 151; Swindler, 1:244-248)

Gadsden Purchase

30 Dec 1853
Gadsden Purchase settled the boundary dispute between the United States and Mexico and established the international line at its present location. (U.S. Stat., vol. 10, pp. 1031-1037; Van Zandt, 11, 29, 162)
04 Aug 1854
Area acquired in the Gadsden Purchase became non-county area when it was officially added to New Mexico Territory without being assigned to a county. (U.S. Stat., vol. 10, ch. 245[1854]/p. 575; Van Zandt, 162; Walker and Bufkin, 21-22)

GILA

08 Feb 1881
GILA created by Arizona Territory from MARICOPA and PINAL. (Ariz. Terr. Laws 1881, 11th assy./ pp. 14-17)
12 Mar 1885
GILA exchanged with GRAHAM. (Ariz. Terr. Laws 1885, 13th assy./ p. 215)
21 Mar 1889
GILA gained from YAVAPAI. (Ariz. Terr. Laws 1889, 15th assy./ pp. 49-52)
19 Mar 1891
GILA gained from YAVAPAI. (Ariz. Terr. Laws 1891, 16th assy./ pp. 102-103)

GRAHAM

10 Mar 1881
GRAHAM created by Arizona Territory from APACHE and PIMA. (Ariz. Terr. Laws 1881, 11th assy./ pp. 155-157)
12 Mar 1885
GRAHAM exchanged with GILA. (Ariz. Terr. Laws 1885, 13th assy./ p. 215)
17 Mar 1897
Boundary between GRAHAM and APACHE clarified [no change]. (Ariz. Terr. Laws 1897, 19th assy./ p. 67)
10 Mar 1909
GRAHAM lost to creation of GREENLEE. (Ariz. Terr. Laws 1909, 25th assy./ pp. 43-56)

GREENLEE

10 Mar 1909
GREENLEE created by Arizona Territory from GRAHAM. (Ariz. Terr. Laws 1909, 25th assy./ pp. 43-56)

LA PAZ

27 Apr 1983
LA PAZ created from YUMA. (Ariz. Laws 1983, 36th assy., ch. 291/pp. 1089-1094)

MARICOPA

14 Feb 1871
MARICOPA created by Arizona Territory from YAVAPAI. (Ariz. Terr. Laws 1871, 6th assy./ pp. 53-54)
14 Feb 1873
MARICOPA gained from PIMA. (Ariz. Terr. Laws 1873, 7th assy./ p. 87)
01 Feb 1875
MARICOPA lost to creation of PINAL. (Ariz. Terr. Laws 1875, 8th assy./ pp. 19-20)
31 Jan 1877
MARICOPA gained from YAVAPAI, and lost small area along the Gila River to PIMA. (Ariz. Terr. Laws 1877, 9th assy./ pp. 12-13)
08 Feb 1881
MARICOPA lost to creation of GILA. (Ariz. Terr. Laws 1881, 11th assy./ pp. 14-17)

MESILLA (proposed)

05 Apr 1860
An unofficial convention held in Tucson established a provisional government, declared the creation of the Territory of Arizona from all that part of New Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and authorized the creation of MESILLA (proposed). Congress failed to recognize the new territory and its proposed counties [no change]. (Sacks, 36, 151; Swindler, 1:244-248)

Mexico

24 Aug 1821
Mexico gained its independence from Spain; present Arizona became part of the Republic of Mexico. (Beers, 100; "Mexican War of Independence," New Handbook of Texas, 4:698)
04 Jul 1848
Treaty of Guadalupe-Hidalgo ended the war between Mexico and the United States. Area ceded by Mexico became Unorganized Federal Territory in the United States; included all of present California, Nevada, and Utah, and parts of present Arizona, Colorado, New Mexico, and Wyoming. Mexico retained parts of present Arizona and New Mexico; Part of the international boundary was in dispute. Map shows only the part of Mexico in present Arizona. (U.S. Stat., vol. 9, pp. 922-943; Parry, 102: 29-59; Van Zandt, 11, 28-29; Walker and Bufkin, 19, 20A)
13 Dec 1850
The portion of present Arizona located south of the boundary defined in the Treaty of Guadalupe-Hidalgo was part of Mexico. Faulty geographic information on the Disturnell map referenced in the treaty led to a dispute between the United States and Mexico over the exact location and extent of the international boundary. Map shows only the part of Mexico in present Arizona. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
09 Jan 1852
The parts of present Arizona and New Mexico located south of the boundary defined in the Treaty of Guadalupe-Hidalgo were part of Mexico; dispute between the United States and Mexico over the exact location and extent of the international boundary continued. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
30 Dec 1853
Gadsden Purchase settled the boundary dispute between the United States and Mexico and established the international line at its present location. (U.S. Stat., vol. 10, pp. 1031-1037; Van Zandt, 11, 29, 162)

MOHAVE

10 Nov 1864
MOHAVE created as one of four original counties in Arizona Territory; included part of present Nevada. (Howell Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
22 Dec 1865
MOHAVE lost to creation of PAH-UTE (extinct). (Ariz. Terr. Laws 1865, 2d assy./ pp. 19-20)
05 May 1866
MOHAVE lost when the United States transferred a portion of northwestern Arizona Territory to the state of Nevada. Arizona twice petitioned Congress to repeal the act and did not recognize the change until 18 February 1871. (U.S. Stat., vol. 14, ch. 73[1866]/p. 43; Sacks, 25; Van Zandt, p. 158, 165)
18 Feb 1871
MOHAVE gained all of PAH-UTE (extinct) when the law creating PAH-UTE was repealed. New definition for MOHAVE implicitly acknowledged the change made to the Arizona - Nevada line on 5 May 1866. (Ariz. Terr. Laws 1871, 6th assy./ p. 87)
06 Mar 1883
MOHAVE exchanged with YAVAPAI. (Ariz. Terr. Laws 1883, 12th assy./ p. 171)
24 Mar 1960
MOHAVE boundary with the state of Nevada was redefined as part of an interstate compact to account for changes in the course of the Colorado River. The adjusted state line apparently had a minor effect on the boundary between MOHAVE and CLARK (Nevada) [not mapped]. (Ariz. Laws 1960, 24th leg., 2d reg. sess., ch. 69/pp. 174-180)
02 Apr 1963
MOHAVE boundary with the state of California was redefined as part of an interstate compact to account for changes in the course of the Colorado River [not mapped]. (Ariz. Laws 1963, 25th leg., 1st reg. sess., ch. 77/ pp. 142-150)

NAVAJO

21 Mar 1895
NAVAJO created by Arizona Territory from APACHE. (Ariz. Terr. Laws 1895, 18th assy./ pp. 96-105)

New Mexico Territory (non-county area)

13 Dec 1850
The United States created New Mexico Territory from Unorganized Federal Territory (land ceded by Mexico in the Treaty of Guadalupe-Hidalgo), and from land purchased from the state of Texas; included most of present Arizona and New Mexico, and parts of present Colorado and Nevada. Faulty geographic information on the Disturnell map referenced in the treaty led to a dispute between the United States and Mexico over the exact location and extent of the international boundary. All that portion of New Mexico Territory lying outside the boundaries of the seven original counties established under Kearny's Code became non-county area; included most of present Arizona and New Mexico, and parts of present Colorado and Nevada. The portion of Arizona south of the Gila River remained part of Mexico. Maps shows only the part of New Mexico Territory in present Arizona and Nevada. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
09 Jan 1852
Non-county area in New Mexico lost to creation of DOŅA ANA (N.M.) and SOCORRO (N.M.), and lost to BERNALILLO (N.M.), RIO ARRIBA (N.M.), SAN MIGUEL (N.M.), SANTA ANA (N.M.), TAOS (N.M.), and VALENCIA (N.M.); all included part of present Arizona; Non-county area eliminated. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 291)
04 Aug 1854
Non-county area was created in New Mexico Territory when the land acquired by the United States in the Gadsden Purchase was officially added to the territory without being assigned to a county. Most of the non-county area was located in present Arizona. (U.S. Stat., vol. 10, ch. 245[1854]/p. 575; Van Zandt, 162; Walker and Bufkin, 21-22)
03 Feb 1855
Non-county area in New Mexico Territory lost to DONA ANA (N.M.); Non-county area eliminated. (N.M. Terr. Laws 1854, 4th assy. /p. 57)

PAH-UTE (extinct)

22 Dec 1865
PAH-UTE (extinct) created by Arizona Territory from MOHAVE; included part of present Nevada. (Ariz. Terr. Laws 1865, 2d assy./ pp. 19-20)
05 May 1866
PAH-UTE (extinct) lost when the United States transferred a portion of northwestern Arizona Territory to the state of Nevada. Arizona twice petitioned Congress to repeal the act and did not recognize the change until 18 February 1871. (U.S. Stat., vol. 14, ch. 73[1866]/p. 43; Sacks, 25; Van Zandt, p. 158, 165)
18 Feb 1871
PAH-UTE (extinct) lost all territory to MOHAVE when the law creating PAH-UTE was repealed; PAH-UTE eliminated. (Ariz. Terr. Laws 1871, 6th assy./ p. 87)

PIMA

10 Nov 1864
PIMA created as one of four original counties in Arizona Territory. (Howell Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
14 Feb 1873
PIMA lost to MARICOPA. (Ariz. Terr. Laws 1873, 7th assy./ p. 87)
01 Feb 1875
PIMA lost to creation of PINAL and was divided into two parts until 9 February 1877. (Ariz. Terr. Laws 1875, 8th assy./ pp. 19-20)
31 Jan 1877
PIMA gained a small area along the Gila River from MARICOPA. (Ariz. Terr. Laws 1877, 9th assy./ pp. 12-13)
09 Feb 1877
PIMA lost to PINAL. Area lost was the part of PIMA that had been separated from main body of the county on 1 February 1875. (Ariz. Terr. Laws 1877, 9th assy./ pp.108-109)
01 Feb 1881
PIMA lost to creation of COCHISE. (Ariz. Terr. Laws 1881, 11th assy./ pp. 4-7)
10 Mar 1881
PIMA lost to creation of GRAHAM. (Ariz. Terr. Laws 1881, 11th assy./ pp. 155-157)
15 Mar 1899
PIMA lost to creation of SANTA CRUZ. (Ariz. Terr. Laws 1899, 20th assy./ pp. 49-57)
02 May 1973
PIMA boundaries redefined [no change]. (Ariz. Laws 1973, 31st leg., 1st reg. sess., ch. 101/ pp. 596-597)

PINAL

01 Feb 1875
PINAL created by Arizona Territory from MARICOPA and PIMA. (Ariz. Terr. Laws 1875, 8th assy./ pp. 19-20)
09 Feb 1877
PINAL gained from PIMA. Area gained was the part of PIMA that had been separated from main body of the county on 1 February 1875. (Ariz. Terr. Laws 1877, 9th assy./ pp. 108-109)
08 Feb 1881
PINAL lost to creation of GILA. (Ariz. Terr. Laws 1881, 11th assy./ pp. 14-17)

RIO ARRIBA (N.M.)

22 Sep 1846
RIO ARRIBA (N.M.) established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852
RIO ARRIBA (N.M.) gained from SAN MIGUEL (N.M.), SANTA ANA (N.M.), SANTA FE (N.M.) and non-county area, and exchanged with TAOS (N.M.) when all counties redefined; included parts of present Arizona, Nevada and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 291)
24 Feb 1863
RIO ARRIBA (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

SAN JUAN (N.M. Territory, original, extinct)

12 Jan 1861
SAN JUAN (N.M. Territory, original, extinct) created by New Mexico Territory from TAOS (N.M.); included parts of present Arizona, New Mexico, and Nevada. (N.M. Terr. Laws 1860-1861, 10th assy. /p. 16)
18 Jan 1862
SAN JUAN (N.M. Territory, original, extinct) eliminated when it lost all territory to TAOS (N.M.)
(N.M. Terr. Laws 1861-1862, 11th assy. /p. 16)

SANTA ANA (N.M. Territory, extinct)

22 Sep 1846
SANTA ANA (N.M. Territory, extinct) established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852
SANTA ANA (N.M. Territory, extinct) gained from BERNALILLO (N.M.) and non-county area, exchanged with SANTA FE (N.M.), and lost to RIO ARRIBA (N.M.) when all counties redefined; included parts of present Arizona, Nevada, and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 292)
24 Feb 1863
SANTA ANA (N.M. Territory, extinct) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

SANTA CRUZ

15 Mar 1899
SANTA CRUZ created by Arizona Territory from PIMA. (Ariz. Terr. Laws 1899, 20th assy./ pp. 49-57)
14 Mar 1968
SANTA CRUZ lost to COCHISE when the boundary was redefined to run along the east line of range 18 east. (Ariz. Laws 1968, 28th leg., 1st reg. sess., ch. 82/ pp. 180-182)

SOCORRO (N.M.)

09 Jan 1852
SOCORRO (N.M.) created by New Mexico Territory from non-county area; included parts of present Arizona and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 1st sess./p. 119; N.M. Terr. Laws 1851, 1st assy., 2d sess. /pp. 266, 292)
24 Feb 1863
SOCORRO (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

TAOS (N.M.)

22 Sep 1846
TAOS (N.M.) established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852
TAOS (N.M.) gained from non-county area, and exchanged with RIO ARRIBA (N.M.) and SAN MIGUEL (N.M.) when all counties redefined; included parts of present Arizona, Colorado, Nevada and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 291)
01 Feb 1860
TAOS (N.M.) lost to creation of MORA (N.M.); the part of TAOS in present Arizona was unchanged. (N.M. Terr. Laws 1859-1860, 9th assy. /p. 76)
12 Jan 1861
TAOS (N.M.) lost to creation of SAN JUAN (N.M. Territory, original, extinct). (N.M. Terr. Laws 1860-1861, 10th assy. /p. 16)
28 Feb 1861
TAOS (N.M.) lost to creation of Colorado Territory; the part of TAOS in present Arizona was unchanged. (U.S. Stat., vol. 12, pp. 172-177; Van Zandt, 141-144)
18 Jan 1862
TAOS (N.M.) gained all of SAN JUAN (N.M. Territory, original, extinct); SAN JUAN eliminated. (N.M. Terr. Laws 1861-1862, 11th assy. /p. 16)
24 Feb 1863
TAOS (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

Unorganized Federal Territory

04 Jul 1848
Treaty of Guadalupe-Hidalgo ended the war between Mexico and the United States. Area ceded by Mexico became Unorganized Federal Territory (non-county area) in the United States; included all of present California, Nevada, and Utah, and parts of present Arizona, Colorado, New Mexico, and Wyoming. Part of the international boundary was in dispute. Map shows only the part Unorganized Federal Territory in present Arizona. (U.S. Stat., vol. 9, pp. 922-943; Parry, 102: 29-59; Van Zandt, 11, 28-29; Walker and Bufkin, 19, 20A)
13 Dec 1850
The United States created New Mexico Territory from Unorganized Federal Territory and land purchased from the state of Texas; all that portion of Unorganized Federal Territory lying outside the boundaries of the seven original counties established under Kearny's Code became non-county area in New Mexico Territory. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)

VALENCIA (N.M.)

22 Sep 1846
VALENCIA (N.M.) established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852
VALENCIA (N.M.) gained from non-county area, lost to creation of SOCORRO (N.M.), and lost to BERNALILLO (N.M.) when all counties redefined; included parts of present Arizona, Nevada, and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 292)
24 Feb 1863
VALENCIA (N.M.) eliminated from Arizona when Arizona Territory was created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)

YAVAPAI

10 Nov 1864
YAVAPAI created as one of four original counties in Arizona Territory. (Howell Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
14 Feb 1871
YAVAPAI lost to creation of MARICOPA. (Ariz. Terr. Laws 1871, 6th assy./ pp. 53-54)
31 Jan 1877
YAVAPAI lost to MARICOPA. (Ariz. Terr. Laws 1877, 9th assy./ pp. 12-13)
14 Feb 1879
YAVAPAI lost to creation of APACHE. (Ariz. Terr. Laws 1879, 10th assy./ pp. 96-97)
06 Mar 1883
YAVAPAI exchanged with MOHAVE. (Ariz. Terr. Laws 1883, 12th assy./ p. 171)
21 Mar 1889
YAVAPAI lost to GILA. (Ariz. Terr. Laws 1889, 15th assy./ pp. 49-52)
19 Feb 1891
YAVAPAI lost to creation of COCONINO. (Ariz. Terr. Laws 1891, 16th assy./ pp. 26-34)
19 Mar 1891
YAVAPAI lost to GILA. (Ariz. Terr. Laws 1891, 16th assy./ pp. 102-103)

YUMA

10 Nov 1864
YUMA created as one of four original counties in Arizona Territory. (Howell Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
02 Apr 1963
YUMA boundary with the state of California was redefined as part of an interstate compact to account for changes in the course of the Colorado River [not mapped]. (Ariz. Laws 1963, 25th leg., 1st reg. sess., ch. 77/ pp. 142-150)
27 Apr 1983
YUMA lost to creation of LA PAZ. (Ariz. Laws 1983, 36th assy., ch. 291/pp. 1089-1094)