Wyoming: Consolidated Chronology of State and County Boundaries

30 April 1803

The United States purchased Louisiana from France, taking formal possession on 20 December 1803; boundaries were not clearly defined, but included the western half of the Mississippi drainage basin (from the Mississippi River to the Rocky Mountains). It included the eastern portion of present Wyoming. (Parry, 57:27–40; Van Zandt, 23–26)

1 October 1804

The United States divided the Louisiana Purchase at the parallel of 33 degrees north latitude into the District of Louisiana and Orleans Territory. The portion of present Wyoming east of the Rocky Mountains became part of the District of Louisiana; the District was not fully organized and was attached to Indiana Territory for administrative and judicial purposes. ST. LOUIS (Mo.) District was created by the District of Louisiana to include a vast area between the Mississippi River and the Rocky Mountains, which encompassed all or part of eight present states. That part of present Wyoming within the District of Louisiana was part of ST. LOUIS District. (U.S. Stat., vol. 2, ch. 38 [1804]/pp. 283–289; Terr. Papers U.S., 13:51–52)

The United States claimed the Oregon Country, including that part of present Wyoming west of the Continental Divide, based on American exploration of the Northwest. No boundaries were defined, and Spain also claimed the area. (Paullin, 36–37, pl. 49)

4 July 1805

The District of Louisiana was renamed Louisiana Territory and was fully organized as a separate territory. ST. LOUIS (Mo.) District became a district (county) in Louisiana Territory; boundaries were unchanged. (U.S. Stat., vol. 2, ch. 31 [1805]/pp. 331–332)

7 December 1812

Louisiana Territory was renamed Missouri Territory. Most of ST. LOUIS (Mo.) reverted to non-county area in Missouri Territory, including the part in present Wyoming; ST. LOUIS (Mo.) eliminated from present Wyoming. (Terr. Papers U.S., 14:599–601; U.S. Stat., vol. 2, ch. 95 [1812]/pp. 743–747)

20 October 1818

A Convention of Commerce between Great Britain and the United States established the parallel of 49 degrees north latitude, from the Lake of the Woods to the Rocky Mountains, as the northern boundary of the United States and the southern boundary of the British possessions; the northern boundary of Missouri Territory was established at 49 degrees north latitude. The area within present Wyoming was unchanged. (Parry, 69:293–297)

22 February 1819

The Adams-Onis Treaty between the United States and Spain established the southern and western boundaries of the United States territory south of the parallel of 42 degrees north latitude. That part of present Wyoming south of 42 degrees north latitude and west of a line running north from the headwaters of the Arkansas River in present Colorado came under Spanish control; the southern boundary of the Oregon Country was set at 42 degrees north latitude; and the boundary of Missouri Territory was altered. (Parry, 70:1–30; Van Zandt, 26–27)

10 August 1821

Missouri Territory was eliminated upon the creation of the state of Missouri. All that part of the former Territory north and west of the state of Missouri, including part of present Wyoming, became unorganized federal territory. (U.S. Stat., vol. 3, ch. 22 [1820]/pp. 545–548; U.S. Stat., vol. 3, res. 1 [1821]/p. 645; Van Zandt, 117)

24 August 1821

Mexico gained its independence from Spain; that part of present Wyoming that had been under the authority of Spain came under the control of Mexico. ("Mexican War of Independence," New Handbook of Texas, 4:698)

2 March 1836

Texas declared its independence from Mexico. The Republic of Texas claimed part of the area of present Wyoming south of 42 degrees north latitude. ("Republic of Texas," New Handbook of Texas, 5:537–538; Swindler, 9:247, 249)

19 December 1836

BEXAR (Texas) boundaries were implicitly expanded to cover all non-county area in the Republic of Texas when the boundaries of the Texas Republic were defined. BEXAR included territory in present Texas, Colorado, Kansas, New Mexico, Oklahoma, and part of present southern Wyoming. Changes in BEXAR boundary between December 1836 and March 1848 did not affect the area within present Wyoming and are not mapped. (Texas Repub. Laws 1836, 1st cong./p. 133)

5 July 1843

CHAMPOEG District (now MARION [Ore.]) created by the Oregon Territory Provisional Government as one of four original districts (later counties); included territory in present Oregon, Idaho, and all that part of present Wyoming north of 42 degrees north latitude and west of the Rocky Mountains. (Holman, 7–9; Swindler, 8:195)

19 December 1845

CHAMPOEG (now MARION [Ore.]) lost to CLACKAMAS (Ore.) along CHAMPOEG's northern border. Area within present Wyoming was unchanged [change too small to map at this scale]. (Ore. Laws, 1843–1849, pp. 36–37)

29 December 1845

The United States Congress admitted Texas to the Union; state of Texas continued to claim part of present Wyoming. (U.S. Stat., vol. 9, res. 1[1846]/p. 108)

15 June 1846

Treaty with Great Britain established the parallel of 49 degrees north latitude, from the Rocky Mountains to the Pacific Ocean, as the northern boundary of the United States; ended Great Britain's claim to the Oregon Country. (U.S. Stat., vol. 9, pp. 869–870; Van Zandt, 11, 18)

28 December 1847

LINN (Ore.) created by the Oregon Territory Provisional Legislature from CHAMPOEG (now MARION [Ore.]). LINN included territory in present Oregon, Idaho, and all that part of present Wyoming north of 42 degrees north latitude and west of the Rocky Mountains. CHAMPOEG eliminated from present Wyoming. (Ore. Laws, 1843–1849, pp. 55–56)

15 March 1848

SANTA FE (Texas, extinct) created by the state of Texas from BEXAR (Texas). SANTA FE included territory in present Texas, Colorado, Kansas, New Mexico, Oklahoma, and part of present southern Wyoming; only the portion in Wyoming is mapped here. SANTA FE boundaries changed on 31 December 1849, but the area within present Wyoming was unchanged. BEXAR eliminated from present Wyoming. (Texas Laws 1847, 2d reg. sess., ch. 87/p. 95)

4 July 1848

Treaty of Guadalupe-Hidalgo ended the Mexican War between the United States and Mexico. Mexico ceded territory that included part of present southwestern Wyoming to the United States. This area was unorganized federal territory (non-county area). (Parry, 102:29–59; U.S. Stat., vol. 9, pp. 922–943; Van Zandt, 11, 28)

14 August 1848

The United States created Oregon Territory following the 1846 settlement of boundary disputes with Great Britain over the extent of the Oregon Country. That part of present Wyoming north of 42 degrees north latitude and west of the Rocky Mountains officially became part of Oregon Territory. (U.S. Stat., vol. 9, ch. 67[1848]/pp. 323–331; Van Zandt, 153)

9 September 1850

The United States created Utah Territory from the territory ceded by Mexico in the Treaty of Guadalupe-Hidalgo (1848), from territory to be purchased from the state of Texas in December 1850, and from unorganized federal territory. The southwestern section of present Wyoming became part of Utah Territory. That part of SANTA FE (Texas, extinct) in present Wyoming was included in the area organized as Utah Territory, although the purchase of the area by the United States was not officially approved until 13 December 1850. SANTA FE effectively eliminated from present Wyoming. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446–452 and ch. 51[1850]/pp. 453–458; Van Zandt, 159)

13 December 1850

The United States purchased territory in present Colorado, Kansas, New Mexico, Oklahoma, and Wyoming from the state of Texas; Texas and SANTA FE (Texas, extinct) officially eliminated from present Wyoming. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446–452 and appendix, sec. 10/pp. 1005–1006; Van Zandt, 122)

04 January 1851

Non-county area created in Oregon Territory from LINN (Ore.); anticipated creation of LANE (Ore.) on 28 January 1851. Non-county area included territory in present Oregon, Idaho and Wyoming. (Ore. Terr. Laws 1850, 2d sess., pp. 33–34)

28 January 1851

LANE (Ore.) created by Oregon Territory from BENTON (Ore.) and LINN (Ore.). LANE included territory in present Oregon, Idaho, and most of present Wyoming north of 42 degrees north latitude and west of the Rocky Mountains. (Ore. Terr. Laws 1850, 2d sess., loc., pp. 32–34)

7 January 1852

LANE (Ore.) lost small area to creation of DOUGLAS (Ore.); area within present Wyoming was unchanged. (Ore. Terr. Laws 1851, 3d sess., p. 18)

3 March 1852

GREEN RIVER (Utah Terr., extinct) created by Utah Territory from non-county area; included territory in present Utah, Colorado, and the southwestern section of present Wyoming. GREEN RIVER not fully organized, attached to GREAT SALT LAKE (now SALT LAKE [Utah]) "for election, revenue, and judicial purposes." (Utah Terr. Laws 1851, 1st sess., sec. 4/pp. 162–163)

22 December 1853

LANE (Ore.) exchanged with DOUGLAS (Ore.) and UMPQUA (Ore., extinct); area within present Wyoming was unchanged. (Ore. Terr. Laws 1853, 5th sess., spec., p. 13)

11 January 1854

WASCO (Ore.) created by Oregon Territory from CLACKAMAS (Ore.), JACKSON (Ore.), LANE (Ore.), LINN (Ore.), and MARION (Ore.); included territory in present Oregon, Idaho, Montana, and all that part of present Wyoming north of 42 degrees north latitude and west of the Rocky Mountains. LANE and LINN eliminated from present Wyoming. (Ore. Terr. Laws 1853, 5th sess., spec., pp. 26–27)

13 January 1854

GREEN RIVER (Utah Terr., extinct) gained from GREAT SALT LAKE (now SALT LAKE [Utah]), SANPETE (Utah), and UTAH (Utah); lost to DAVIS (Utah) and lost to creation of SUMMIT (Utah). (Utah Terr. Laws 1853, 3d sess., pp. 14–15)

SUMMIT (Utah) created by Utah Territory from GREEN RIVER (Utah Terr., extinct) and GREAT SALT LAKE (now SALT LAKE [Utah]); SUMMIT included territory in present Utah and Wyoming. SUMMIT not fully organized, attached to GREAT SALT LAKE "for election, revenue, and judicial purposes." (Utah Terr. Laws 1853, 3d sess., pp. 14–15)

30 May 1854

The United States created Nebraska Territory from unorganized federal territory; included all of present Wyoming east of the Continental Divide. (U.S. Stat., vol. 10, ch. 59[1854]/pp. 277–290; Van Zandt, 136)

15 June 1854

GREEN RIVER (Utah Terr., extinct) fully organized, detached from GREAT SALT LAKE (now SALT LAKE [Utah]). (Gowans and Campbell, 63)

5 January 1856

CACHE (Utah) created by Utah Territory from SUMMIT (Utah) and WEBER (Utah); CACHE included territory in present Utah and Wyoming. CACHE not fully organized. (Utah Terr. Laws 1855, 5th sess., sec. 5/p. 6)

14 January 1857

Boundary between WASCO (Ore.) and MULTNOMAH (Ore.) adjusted near the Columbia River [change too small to map]. (Ore. Terr. Laws 1856, 8th sess., pp. 78–79)

4 April 1857

CACHE (Utah) fully organized. (Ricks, 90)

22 December 1857

GREEN RIVER (Utah Terr., extinct) disorganized and attached to GREAT SALT LAKE (now SALT LAKE [Utah]) "for election, revenue and judicial purposes" because most settlers had left the area. (Utah Terr. Laws 1857, 7th sess., p. 1)

17 January 1859

GREEN RIVER (Utah Terr., extinct) reorganized, detached from GREAT SALT LAKE (now SALT LAKE [Utah]). (Utah Terr. Laws 1858, 8th sess., ch. 11/pp. 19–20)

14 February 1859

State of Oregon created from Oregon Territory; Oregon Territory eliminated. That part of the former Oregon Territory east of the state of Oregon, including part of present Wyoming west of the Rocky Mountains, became part of Washington Territory. WASCO (Ore.) eliminated from present Wyoming when state of Oregon was created. (U.S. Stat., vol. 11, ch. 33[1859]/pp. 383–384)

9 January 1861

SHOSHONE (Idaho) created by Washington Territory from SPOKANE (Wash. Terr., original, extinct) and non-county area; included territory in present Idaho, Montana, and that part of present Wyoming west of the Rocky Mountains and north of 42 degrees north latitude. SHOSHONE not fully organized, attached to WALLA WALLA (Wash.) "for judicial purposes." (Wash. Terr. Laws 1860, 8th leg., pp. 13–14)

28 February 1861

The United States created Colorado Territory from Nebraska, New Mexico, and Utah Territories, and from the remnant of Kansas Territory. GREEN RIVER (Utah Terr., extinct) lost to Colorado Territory; area within present Wyoming was unchanged. (U.S. Stat., vol. 12, ch. 59[1861]/pp. 172–177)

2 March 1861

The United States created Dakota Territory from Nebraska Territory and Unorganized Federal Territory; included the northern part of present Wyoming east of the Continental Divide. (Dak. Terr. Laws 1862, 1st sess., pp. 21–28; U.S. Stat., vol. 12, ch. 86[1861]/pp. 239–244; Van Zandt, 134, 136–137)

Nebraska Territory gained from Utah and Washington Territories, lost to creation of Dakota Territory. Nebraska Territory included the southern part of present Wyoming east of 33 degrees longitude west of Washington, D.C. GREEN RIVER (Utah Terr., extinct) lost to Nebraska Territory when Nebraska Territory gained area in present Wyoming from Utah Territory. SHOSHONE (Idaho) lost to Nebraska Territory when Nebraska Territory gained area in present Wyoming from Washington Territory. (U.S. Stat., vol. 12, ch. 86[1861]/pp. 239–244; Van Zandt, 134, 136–137)

4 March 1861

SUMMIT (Utah) fully organized, detached from GREAT SALT LAKE (now SALT LAKE [Utah]). (County Record Book A, p. 1)

20 December 1861

IDAHO (Idaho) created by Washington Territory from SHOSHONE (Idaho); included territory in present Idaho, Montana, and Wyoming. SHOSHONE eliminated from present Wyoming. (Wash. Terr. Laws 1861, 9th leg., pp. 3–5)

17 January 1862

CACHE (Utah) gained from SUMMIT (Utah), exchanged with GREEN RIVER (Utah Terr., extinct), lost to WEBER (Utah), and lost small area to creation of MORGAN (Utah). (Utah Terr. Laws 1861, 11th sess., sec. 16/p. 50)

GREEN RIVER (Utah Terr., extinct) exchanged with CACHE (Utah), lost to SUMMIT (Utah) and SANPETE (Utah), and lost to creation of WASATCH (Utah). (Utah Terr. Laws 1861, 11th sess., sec. 17/p. 50)

SUMMIT (Utah) gained from GREAT SALT LAKE (now SALT LAKE [Utah]) and GREEN RIVER (Utah Terr., extinct), lost to creation of MORGAN (Utah) and WASATCH (Utah), and lost to CACHE (Utah) and WEBER (Utah). (Utah Terr. Laws 1861, 11th sess., sec. 14/pp. 49–50)

12 January 1863

BOISE (Idaho) created by Washington Territory from IDAHO (Idaho); included territory in present Idaho and Wyoming. IDAHO eliminated from present Wyoming. (Wash. Terr. Laws 1862, 10th leg., pp. 3–4)

3 March 1863

The United States created Idaho Territory from Dakota, Nebraska, and Washington Territories; Dakota and Nebraska Territories eliminated from present Wyoming. BOISE (Idaho) became a county in Idaho Territory. (U.S. Stat., vol. 12, ch. 117[1863]/pp. 808–814; Van Zandt, 156)

31 December 1863

OWYHEE (Idaho) created by Idaho Territory from BOISE (Idaho) and non-county area; included territory in present Idaho and most of present Wyoming west of the Rocky Mountains and south of the Snake River. (Idaho Terr. Laws 1863, 1st sess., p. 624)

16 January 1864

OGALALA (Idaho Terr., extinct) created by Idaho Territory from non-county area. OGALALA was located in the eastern half of present Wyoming. (Idaho Terr. Laws 1863, 1st sess., sec. 9/p. 677)

RICHLAND (now RICH [Utah]) created by Utah Territory from CACHE (Utah); RICHLAND included territory in present Utah and Wyoming. RICHLAND not fully organized. CACHE eliminated from present Wyoming. (Utah Terr. Laws 1863, 13th sess., pp. 18–19)

YELLOWSTONE (Idaho Terr., extinct) created by Idaho Territory from non-county area. YELLOWSTONE was located entirely within present Wyoming. (Idaho Terr. Laws 1863, 1st sess., sec. 10/p. 677)

22 January 1864

ONEIDA (Idaho) created by Idaho Territory from BOISE (Idaho) and OWYHEE (Idaho); included territory in present Idaho and most of present Wyoming west of the Rocky Mountains. BOISE and OWYHEE eliminated from present Wyoming. (Idaho Terr. Laws 1863, 1st sess., p. 625)

5 May 1864

RICHLAND (now RICH [Utah]) fully organized. (Parson, 274)

26 May 1864

Dakota Territory gained from Idaho Territory; most of present Wyoming became part of Dakota Territory. ONEIDA (Idaho) lost to Dakota Territory when Dakota Territory gained from Idaho Territory. OGALALA and YELLOWSTONE eliminated from Idaho Territory and present Wyoming. (U.S. Stat., vol. 13, ch. 95[1864], sec. 18/p. 92; Van Zandt, 134–136, 156–157)

9 January 1867

LARAMIE created by Dakota Territory from non-county area; included all of present Wyoming that was then part of Dakota Territory, plus a small area of present Montana. (Dak. Terr. Laws 1866, 6th sess., ch. 14/p. 43)

27 December 1867

CARTER (now SWEETWATER) created by Dakota Territory from LARAMIE; included a small area of present Montana. CARTER not fully organized, attached to LARAMIE "for representative and judicial purposes." (Dak. Terr. Laws 1867, 7th sess., ch. 7/pp. 122–123)

3 January 1868

LARAMIE boundaries redefined [no change]. (Dak. Terr. Laws 1867, 7th sess., ch. 8/pp. 123–124)

January 1868

In early 1868, CARTER (now SWEETWATER) fully organized, detached from LARAMIE. (Trenholm, 1:331)

29 January 1868

RICHLAND renamed RICH (Utah). (Utah Terr. Laws 1868, 17th sess., ch. 2/p. 1)

25 July 1868

The United States created Wyoming Territory with present boundaries from Dakota, Idaho, and Utah Territories. Wyoming Territorial Legislature did not meet until October 1869, and Dakota Territory continued to govern Wyoming until 19 May 1869. GREEN RIVER (Utah Terr., extinct), ONEIDA (Idaho), RICH (Utah), and SUMMIT (Utah) were eliminated from present Wyoming. (Trenholm, 1:83–84; U.S. Stat., vol. 15, ch. 235[1868], secs. 1, 17/pp. 178, 183; Van Zandt, 136, 144)

CARTER (now SWEETWATER) lost small area in present Montana when Wyoming Territory boundaries were defined. (Trenholm, 1:83–84; U.S. Stat., vol. 15, ch. 235[1868], secs. 1, 17/pp. 178, 183; Van Zandt, 136, 144)

16 December 1868

ALBANY created by Dakota Territory from LARAMIE. Error in the definition of ALBANY's western boundary was corrected 13 December 1869 by the Wyoming Territorial Legislature. (Dak. Terr. Laws 1868, 8th sess., ch. 28/p. 311; Trenholm, 1:84, 334)

CARBON created by Dakota Territory from LARAMIE. Error in the definition of CARBON's southern boundary was corrected 1 January 1870 by the Wyoming Territorial Legislature. (Dak. Terr. Laws 1868, 8th sess., ch. 35/p. 321; Trenholm, 1:84, 334)

19 May 1869

Wyoming Territory fully organized; ALBANY, CARBON, CARTER (now SWEETWATER), and LARAMIE became Wyoming Territory counties. (Trenholm, 1:83–84, 334)

1 December 1869

UINTA created by Wyoming Territory from CARTER (now SWEETWATER) and non-county area. CARTER implicitly exchanged non-county areas. (Wyo. Terr. Laws 1869, 1st leg., ch. 34/p. 382; Whitehead, 194)

13 December 1869

ALBANY boundaries clarified; corrected error of 16 December 1868 [no change]. (Wyo. Terr. Laws 1869, 1st leg., ch. 38/p. 388; Whitehead, 198)

CARTER renamed SWEETWATER; boundaries redefined [no change]. (Wyo. Terr. Laws 1869, 1st leg., ch. 35/pp. 383–385; Whitehead, 194–196)

1 January 1870

CARBON gained a half-mile-wide strip of territory from ALBANY all along CARBON's eastern boundary. Mistake in description dating from 16 December 1868 was corrected. (Wyo. Terr. Laws 1869, 1st leg., ch. 37/pp. 387–388; Whitehead, 197)

6 December 1871

Territorial Legislature authorized LARAMIE to gain from ALBANY. On 14 December 1871 the Governor vetoed the bill, but the legislature passed it over the Governor's veto. On 12 November 1872, the Wyoming Territory Supreme Court ruled the act was void and did not comply with the Organic Act of Wyoming Territory [not mapped]. (Wyo. Terr. Laws 1871, 2d leg., pp. 124–125; "Brown v. Nash" and “Union Pacific Railroad Company v. Carr and Boswell,” in Wyoming Rpts., 1:85–103; Homsher, 193–195)

1 March 1872

The United States created America's first national park—Yellowstone. The Park lay mostly in Wyoming Territory, with smaller sections in Montana and Idaho Territories. The Wyoming section of the Park lay in UINTA. (U.S. Stat., vol. 17, ch 24[1872]/pp. 32–33)

8 December 1875

CROOK created by Wyoming Territory from ALBANY and LARAMIE; CROOK not fully organized, attached to ALBANY and LARAMIE "for judicial and all other purposes." (Whitehead, 198–201; "Crook County v. Sheridan County," in Wyoming Rpts., 17:424–467)

PEASE (now JOHNSON) created by Wyoming Territory from ALBANY, CARBON, and SWEETWATER; PEASE not fully organized, attached to ALBANY, CARBON, and SWEETWATER "for judicial and all other purposes." (Whitehead, 199–201)

15 December 1877

CARBON boundaries clarified; explicitly corrected error of 16 December 1868 [no change]. (Wyo. Terr. Laws 1877, 5th leg., p. 19)

13 December 1879

PEASE renamed JOHNSON. (Wyo. Terr. Laws 1879, 6th leg., ch. 31/p. 47)

10 May 1881

JOHNSON fully organized, detached from ALBANY, CARBON, and SWEETWATER. (Trenholm, 1:331)

5 March 1884

FREMONT created by Wyoming Territory from SWEETWATER; FREMONT not fully organized, attached to SWEETWATER "for judicial and all other purposes." (Wyo. Terr. Laws 1884, 8th leg., ch. 46/pp. 66–69)

6 March 1884

The Wyoming Territorial Legislature confirmed that the Wyoming portion of Yellowstone National Park, established 1 March 1872, was part of UINTA. (Wyo. Terr. Laws 1884, 8th leg., ch. 103/pp. 177–183)

6 May 1884

FREMONT fully organized, detached from SWEETWATER. (Trenholm, 1:331)

22 January 1885

CROOK fully organized, detached from ALBANY and LARAMIE. (Trenholm, 1:331)

5 February 1886

CARBON gained from SWEETWATER, lost to ALBANY. (Wyo. Terr. Laws 1886, 9th leg., ch. 5/pp. 5–8)

12 March 1886

LARAMIE boundaries redefined [no change]. (Wyo. Terr. Laws 1886, 9th leg., ch. 105/p. 393)

9 March 1888

CONVERSE created by Wyoming Territory from ALBANY and LARAMIE; CONVERSE not fully organized, attached to ALBANY and LARAMIE for administrative and judicial purposes. (Wyo. Terr. Laws 1888, 10th leg., ch. 90, sec. 60/p. 217)

NATRONA created by Wyoming Territory from CARBON; NATRONA not fully organized, attached to CARBON for administrative and judicial purposes. (Wyo. Terr. Laws 1888, 10th leg., ch. 90, sec. 61/pp. 217–218)

SHERIDAN created by Wyoming Territory from JOHNSON; SHERIDAN not fully organized, attached to JOHNSON for administrative and judicial purposes. (Wyo. Terr. Laws 1888, 10th leg., ch. 90, sec. 62/p. 218; "Crook County v. Sheridan County," in Wyoming Rpts., 17:424–467)

11 May 1888

SHERIDAN fully organized, detached from JOHNSON. (Trenholm, 1:331)

21 May 1888

CONVERSE fully organized, detached from ALBANY and LARAMIE. (Trenholm, 1:331)

12 March 1890

BIG HORN created by Wyoming Territory from FREMONT, JOHNSON, and SHERIDAN; BIG HORN not fully organized, attached to FREMONT, JOHNSON, and SHERIDAN "for judicial, revenue and election purposes." (Wyo. Terr. Laws 1890, 11th leg., ch. 48/pp. 80–83)

WESTON created by Wyoming Territory from CROOK. WESTON not fully organized, attached to CROOK for administrative and judicial purposes. (Wyo. Terr. Laws 1890, 11th leg., ch. 47/pp. 79–80)

11 April 1890

NATRONA fully organized, detached from CARBON. (Trenholm, 1:331)

16 May 1890

WESTON fully organized, detached from CROOK. (Trenholm, 1:331)

10 July 1890

The state of Wyoming was created from Wyoming Territory; Wyoming Territory eliminated. ALBANY, BIG HORN, CARBON, CONVERSE, CROOK, FREMONT, JOHNSON, LARAMIE, NATRONA, SHERIDAN, SWEETWATER, UINTA, and WESTON became counties in the state of Wyoming. (Wyoming Constitution 1889, art. 12 in Swindler, 10:493; U.S. Stat., vol. 26, ch. 664[1890]/pp. 222–226; Van Zandt, 145)

4 January 1897

BIG HORN fully organized, detached from FREMONT, JOHNSON, and SHERIDAN. (Trenholm, 1:331)

15 February 1909

PARK created from BIG HORN; PARK not fully organized, attached to BIG HORN "for judicial, revenue and election purposes." (Wyo. Laws 1909, 10th leg., ch. 19/pp. 23–24)

27 February 1909

CARBON gained small area from FREMONT and exchanged with SWEETWATER when boundaries were adjusted to run on federal land survey lines. NATRONA gained from FREMONT when boundary was adjusted to run on federal land survey lines. (Wyo. Laws 1909, 10th leg., ch. 129/pp. 174–176)

3 January 1911

PARK fully organized, detached from BIG HORN. (Trenholm, 2:518)

21 February 1911

Between February 9 and 20, 1911, seven laws were passed creating new counties and altering county boundaries. On 21 February, the boundaries of all counties created before 9 February were re-described, but this law ignored the new counties created days earlier. These laws were not passed in the intended sequence and mapping them in strict chronological order is not practical. By treating the law of 21 February as the basic structure that the other laws modify, the mapping reflects the intent of the legislature.

ALBANY gained from LARAMIE and former part of LARAMIE (now PLATTE) when boundary was adjusted to run on federal land survey lines; boundary with CARBON was adjusted to run on federal land survey lines. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 1, 3, 8/pp. 102–105, 108)

BIG HORN lost to creation of HOT SPRINGS and WASHAKIE. HOT SPRINGS and WASHAKIE not fully organized, part of HOT SPRINGS and all of WASHAKIE attached to BIG HORN "for judicial, revenue and election purposes." BIG HORN boundaries were redefined to run on federal land survey lines [no change]. Technically, HOT SPRINGS and WASHAKIE had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., chs. 8–9/pp. 7–11 and ch. 77, secs. 2, 6, 9–10/pp. 102–104, 106–107, 109–110)

CAMPBELL created from CROOK and WESTON. CAMPBELL not fully organized, attached to CROOK and WESTON "for judicial, revenue and election purposes." Technically, CAMPBELL had been created on 13 February 1911. (Wyo. Laws 1911, 11th leg., ch. 14/pp. 15–16)

CARBON gained from SWEETWATER, boundary with ALBANY was adjusted to run on federal land survey lines. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 1, 3, 12/pp. 102–105, 111–112)

CONVERSE lost to creation of NIOBRARA. NIOBRARA not fully organized, attached to CONVERSE "for judicial, revenue and election purposes." CONVERSE gained territory along former boundary with LARAMIE; boundaries with JOHNSON, NATRONA, and WESTON adjusted to run on federal land survey lines. Technically, NIOBRARA had been created on 14 February 1911. (Wyo. Laws 1911, 11th leg., ch. 20/pp. 23–24 and ch. 77, secs. 4, 8–9, 14/pp. 105–106, 108–109, 113)

CROOK lost to creation of CAMPBELL. CAMPBELL not fully organized, part attached to CROOK "for judicial, revenue and election purposes." CROOK boundaries redefined to run on federal land survey lines. Technically, CAMPBELL had been created on 13 February 1911. (Wyo. Laws 1911, 11th leg., ch. 14/pp. 15–16 and ch. 77, secs. 5, 7, 11/pp. 106–108, 111)

FREMONT lost to creation of HOT SPRINGS. HOT SPRINGS not fully organized, part attached to FREMONT "for judicial, revenue and election purposes." FREMONT exchanged territory along former boundary with UINTA when boundary was adjusted to run on federal land survey lines. Technically, HOT SPRINGS had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 9/pp. 9–11 and ch. 77, secs. 6, 13/pp. 106–107, 112–113)

GOSHEN created from LARAMIE. GOSHEN not fully organized, attached to LARAMIE "for judicial, revenue and elective purposes." Technically, GOSHEN had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 10/pp. 12–13)

HOT SPRINGS created from BIG HORN, FREMONT, and PARK. HOT SPRINGS not fully organized, attached to BIG HORN, FREMONT, and PARK "for judicial, revenue and election purposes." Technically, HOT SPRINGS had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 9/pp. 9–11)

JOHNSON lost territory along former boundary with CROOK and WESTON when boundaries were redefined to run on federal land survey lines. JOHNSON gained from NATRONA when southern boundary was adjusted to run on federal land survey lines. Boundaries with CONVERSE and SHERIDAN clarified [no change]. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 5, 7, 9, 11, 14/pp. 106–109, 111, 113)

LARAMIE lost to creation of GOSHEN and PLATTE. GOSHEN and PLATTE not fully organized, attached to LARAMIE "for judicial, revenue and elective purposes." LARAMIE lost to ALBANY when boundary was adjusted to run on federal land survey lines. Technically, GOSHEN and PLATTE had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., chs. 7, 10/pp. 6–7, 12–13 and ch. 77, secs. 1, 8/pp. 102–103, 108)

LINCOLN created from UINTA. LINCOLN not fully organized, attached to UINTA "for judicial, revenue and election purposes." Technically, LINCOLN had been created on 20 February 1911. (Wyo. Laws 1911, 11th leg., ch. 67/pp. 93–94)

NATRONA lost to JOHNSON when boundary was adjusted to run on federal land survey lines. Boundary with CONVERSE was adjusted to run on federal land survey lines. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 2, 4, 7, 9/pp. 102–109)

NIOBRARA created from CONVERSE. NIOBRARA not fully organized, attached to CONVERSE "for judicial, revenue and election purposes." Technically, NIOBRARA had been created on 14 February 1911. (Wyo. Laws 1911, 11th leg., ch. 20/pp. 23–24)

PARK lost to creation of HOT SPRINGS. HOT SPRINGS not fully organized, part attached to PARK "for judicial, revenue and election purposes." PARK lost territory in Yellowstone National Park and lost along former boundary with UINTA when boundaries were adjusted to run on federal land survey lines. Technically, HOT SPRINGS had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 9/pp. 9–11 and ch. 77, secs. 10, 13/pp. 109–110, 112–113)

PLATTE created from LARAMIE. PLATTE not fully organized, attached to LARAMIE "for judicial, revenue and elective purposes." Technically, PLATTE had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 7/pp. 6–7)

SHERIDAN lost territory along former boundary with CROOK when boundary was adjusted to run on federal land survey lines. Southern boundary of SHERIDAN was clarified [no change]. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 5, 7, 11/pp. 106–108, 111)

SWEETWATER lost to CARBON, and lost along western boundary to UINTA and former part of UINTA (now LINCOLN) when boundaries were adjusted to run on federal land survey lines. (Wyo. Laws 1911, 11th leg., ch. 77, secs. 12–13/pp. 111–113)

UINTA lost to creation of LINCOLN. LINCOLN not fully organized, attached to UINTA "for judicial, revenue and election purposes." Technically, LINCOLN had been created on 20 February 1911. UINTA lost to Yellowstone National Park, which was removed from county jurisdiction. UINTA gained from SWEETWATER when boundary was adjusted to run on federal land survey lines. (Wyo. Laws 1911, 11th leg., ch. 67/pp. 9394 and ch. 77, secs. 1213/pp. 111–113)

WASHAKIE created from BIG HORN. WASHAKIE not fully organized, attached to BIG HORN "for judicial, revenue and election purposes." Technically, WASHAKIE had been created on 9 February 1911. (Wyo. Laws 1911, 11th leg., ch. 8/pp. 7–9)

WESTON lost to creation of CAMPBELL. CAMPBELL not fully organized, part attached to WESTON "for judicial, revenue and election purposes." The southern boundary of WESTON was adjusted to run on federal land survey lines. Technically, CAMPBELL had been created on 13 February 1911. (Wyo. Laws 1911, 11th leg., ch. 14/pp. 15–16 and ch. 77, secs. 4, 14/pp. 105–106, 113)

That part of Yellowstone National Park located in Wyoming was removed from the jurisdiction of UINTA and PARK, and remained a non-county area outside any county jurisdiction. (Wyo. Laws 1911, 11th leg., ch. 67/pp. 93–94 and ch. 77, sec. 10/pp. 109–110)

23 May 1911

CAMPBELL fully organized, detached from CROOK and WESTON. (Trenholm, 2:518)

6 January 1913

GOSHEN and PLATTE fully organized, detached from LARAMIE. HOT SPRINGS fully organized, detached from BIG HORN, FREMONT, and PARK. LINCOLN fully organized, detached from UINTA. WASHAKIE fully organized, detached from BIG HORN. (Trenholm, 2:518)

8 January 1913

NIOBRARA fully organized, detached from CONVERSE. (Trenholm, 2:518)

15 February 1921

SUBLETTE created from FREMONT and LINCOLN; SUBLETTE not fully organized, attached to FREMONT and LINCOLN "for judicial, revenue and election purposes." (Wyo. Laws 1921, 16th leg., ch. 52/pp. 42–44)

TETON created from LINCOLN; TETON not fully organized, attached to LINCOLN "for judicial, revenue and election purposes." (Wyo. Laws 1921, 16th leg., ch. 53/pp. 45–46; "Budge, et al. v. Board of Commissioners of Lincoln County, et al.," in Wyoming Rpts., 29:35–49)

2 December 1922

TETON fully organized, detached from LINCOLN. (Trenholm, 2:518)

2 January 1923

SUBLETTE fully organized, detached from FREMONT and LINCOLN. (Trenholm, 2:518)

15 February 1923

LINCOLN gained from TETON. Efforts to halt the creation and organization of TETON were denied by the Wyoming Supreme Court in 1923 and 1924. (Wyo. Laws 1923, 17th leg., ch. 21/pp. 34–35; "State ex rel. Budge v. Snyder," in Wyoming Rpts., 30:287–309 and 31:333–355)

7 February 1929

Boundary between JOHNSON and SHERIDAN clarified [no change]. (Wyo. Laws 1929, 20th leg., ch. 18/pp. 23–24)

PARK gained from HOT SPRINGS and gained part of Yellowstone National Park. The rest of Yellowstone National Park in Wyoming remained a non-county area outside county jurisdiction. Mistake in description of PARK would have transferred a small area from TETON to PARK [not mapped; corrected 5 March 1931]. (Wyo. Laws 1929, 20th leg., ch. 22/pp. 26–27)

14 February 1929

TETON gained from LINCOLN and gained part of Yellowstone National Park, thereby placing the remainder of Yellowstone National Park in Wyoming under county jurisdiction. (Wyo. Laws 1929, 20th leg., ch. 42/pp. 50–51)

5 March 1931

HOT SPRINGS gained from PARK. Mistake of 7 February 1929, transferring a small area of TETON to PARK, was corrected [no change]. (Wyo. Laws 1931, 21st leg., ch. 96/pp. 167–168)

6 March 1931

NATRONA gained small areas from CONVERSE in Township 32 North [too small to map]. (Wyo. Laws 1931, 21st leg., ch. 124/pp. 188–189)

27 February 1950

UINTA boundaries redefined [no change]. (Wyo. Laws 1950, 30th leg., spec. sess., ch. 8/p. 16)

14 February 1951

SWEETWATER and UINTA boundaries clarified to reflect a resurvey of townships on the southwestern corner of SWEETWATER and the southeastern corner of UINTA [no mappable change]. (Wyo. Laws 1951, 31st leg., ch. 61, secs. 1–2/pp. 81–83)

20 February 1953

Legislature authorized CONVERSE to gain from ALBANY dependent on local referendum. Error in the description resulted in no referendum being held; Wyoming Supreme Court ordered the law be resubmitted to the Legislature so the boundaries could be correctly established [no change; see 12 July 1955]. (Wyo. Laws 1953, 32d leg., ch. 137/pp. 150–154; "State ex rel. C.A. Fawcett v. Board of the County Commissioners of the County of Albany," in Wyoming Rpts., 73:69–91)

12 July 1955

CONVERSE gained from ALBANY. Act passed 10 February 1955; special election to authorize change was held 12 July 1955. (Wyo. Laws 1955, 33d leg., ch. 74/pp. 60–64; Wyoming Statutes Annotated 2001, 4:378)

8 February 1961

SUBLETTE boundaries clarified [no change]. (Wyo. Laws 1961, 36th leg., ch. 38/pp. 28–30)

9 February 1961

LINCOLN boundaries clarified [no change]. (Wyo. Laws 1961, 36th leg., ch. 43/pp. 32–34)

16 February 1963

LINCOLN and SUBLETTE boundaries clarified [no change]. (Wyo. Laws 1963, 37th leg., ch. 106, secs. 1–2/pp. 143–146)

1 March 1965

LINCOLN gained small area from TETON in Township 39 North, Range 117 West. (Wyo. Laws 1965, 38th leg., ch. 149, sec. 1/pp. 401–402)