User:Golbez/Territorial evolution of Colorado

Colorado Territory was created by the United States on February 28, 1861, from parts of the territories of Nebraska, New Mexico, and Utah, as well as unorganized territory previously attached to Kansas Territory. The territory created its first seventeen counties on November 1, 1861, plus land set aside for an Indian reservation for the Arapaho and Cheyenne. By the time the territory was admitted to the union on August 1, 1876, as the State of Colorado, this number had increased to 26. While Colorado's external borders have never changed, the state has since increased its number of counties to 64.

This list diagrams all changes to the internal borders of Colorado, with one major exception. In 1902, the city of Denver was turned into a consolidated city-county, thus qualifying to appear on this list. However, starting in 1941, Denver began annexing land from the surrounding counties of Adams, Arapahoe, and Jefferson. Many of these annexations are too small to be visible on any map other than professional or government-supplied maps, and thus all changes to Denver are omitted from this list between its first annexation in 1941 and its most recent in 2009. During that time, Denver's borders changed roughly 180 times.

Timeline of Colorado Territory
Colorado Territory was created from parts of the territories of Nebraska, New Mexico, and Utah, as well as unorganized territory previously attached to Kansas Territory. The capital was established at Denver. At this time, no counties were created.
 * February 28, 1861

The initial seventeen counties were created: Arapahoe, Boulder, Clear Creek, Costilla, Douglas, El Paso, Fremont, Gilpin, Guadaloupe, Huerfano, Jefferson, Lake, Larimer, Park, Pueblo, Summit, and Weld. Additionally, a reserve for the Arapaho and Cheyenne was created outside of any county.
 * November 1, 1861

Guadaloupe County was renamed Conejos County.
 * November 7, 1861

Conejos County gained territory from Costilla County.
 * February 24, 1864

Fremont County gained territory from Pueblo County.
 * March 11, 1864

Fremont County gained territory from El Paso and Pueblo counties.
 * February 6, 1866

Las Animas County was created from Huerfano County.
 * February 9, 1866

Saguache County was created from Costilla County.
 * December 19, 1866

Lake County gained territory Fremont County.
 * January 6, 1868

Costilla County gained territory from Las Animas County; Huerfano County gained territory from Costilla and Fremont counties, and exchanged territory with Las Animas County; Pueblo County gained territory from Fremont and Huerfano counties, as well as the Indian Reserve; and the remaining detached areas of Huerfano County became non-county area.
 * January 9, 1868

Bent County was created from Las Animas and Pueblo counties; Greenwood County was created from Pueblo County, the Indian Reserve, and non-county area; and El Paso County gained territory from the Indian Reserve.
 * February 11, 1870

Saguache County gained territory from Lake County.
 * February 9, 1872

Elbert County was created from Douglas and Greenwood counties, as well as the remaining portion of the Indian Reserve; Grand County was created from Summit County.
 * February 2, 1874

Bent County gained all of Greenwood County.
 * February 6, 1874

Hinsdale and La Plata counties were created from Conejos and Lake counties; Rio Grande County was created from Conejos and Costilla counties; and Costilla County gained from Saguache County.
 * February 10, 1874

San Juan County was created from Hinsdale and La Plata counties, and Hinsdale County gained territory from La Plata County.
 * May 1, 1876

Timeline of Colorado
Colorado Territory was admitted to the union as the State of Colorado.
 * August 1, 1876

Ouray County was created from San Juan County.
 * January 18, 1877

Routt County was created from Grand County.
 * January 29, 1877

Custer County was created from Fremont County and non-county area, and Gunnison County was created from Lake County.
 * March 9, 1877

Carbonate County was created from Lake and Summit counties, and Summit County gained territory from Lake County.
 * February 8, 1879

Chaffee County was created from Lake, and Carbonate County was renamed Lake County.
 * February 10, 1879

Rio Grande County exchanged territory with Saguache County.
 * February 12, 1879

Dolores County was created from Ouray County.
 * February 19, 1881

Pitkin County was created from Gunnison County.
 * February 23, 1881

Garfield County was created from Summit County.
 * February 10, 1883

Delta County and Montrose County were created from Gunnison County, and Eagle County was created from Summit County.
 * February 11, 1883

Mesa County was created from Gunnison County.
 * February 14, 1883

Uncompahgre County was created from Gunnison, Montrose, and Ouray counties; Montrose County gained territory from Gunnison.
 * February 27, 1883

Ouray County was renamed San Miguel County, and Uncompahgre County was renamed Ouray County.
 * March 2, 1883

Archuleta County was created from Conejos County.
 * April 14, 1885

Washington County was created from Weld County.
 * February 9, 1887

Logan County was created from Weld County.
 * February 25, 1887

Morgan County was created from Weld County.
 * February 19, 1889

Yuma County was created from Washington County.
 * March 15, 1889

Cheyenne County was created from Bent and Elbert counties, Otero County was created from Bent County, and Rio Blanco County was created from Garfield County.
 * March 25, 1889

Phillips County was created from Logan County.
 * March 27, 1889

Sedgwick County was created from Logan County.
 * April 9, 1889

Kiowa County and Prowers County were created from Bent County, Kit Carson County was created from Elbert County, and Lincoln County was created from Bent and Elbert counties.
 * April 11, 1889

Baca County was created from Las Animas County, and Montezuma County was created from La Plata County.
 * April 16, 1889

Mineral County was created from Hinsdale, Rio Grande, and Saguache counties.
 * March 27, 1893

Teller County was created from El Paso and Fremont counties.
 * March 23, 1899

Adams County and the City and County of Denver were created from Arapahoe County, Colorado, and Arapahoe County was renamed South Arapahoe County.
 * November 15, 1902

South Arapahoe County was renamed Arapahoe County.
 * April 11, 1903

Washington County and Yuma County gained territory from Adams County.
 * May 12, 1903

Archuleta County exchanged territory with Conejos County.
 * April 20, 1905

Park County gained territory from Jefferson County.
 * April 9, 1907

Jackson County was created from Larimer County.
 * May 5, 1909

Moffat County was created from Routt County.
 * February 27, 1911

Crowley County was created from Otero County.
 * May 29, 1911

Alamosa County was created from Conejos and Costilla counties, and Conejos County gained territory from Costilla County.
 * March 8, 1913

Montrose County exchanged territory with Ouray County.
 * March 24, 1913

Ouray County exchanged territory with San Miguel County.
 * April 17, 1917

Dolores County exchanged territory with San Miguel County.
 * March 2, 1923

Routt County gained territory from Garfield and Rio Blanco counties.
 * at some point before 1930

The City and County of Denver performed its first annexation. Over the next six decades, Denver will annex land roughly 180 times from Adams, Arapahoe, and Jefferson counties. While these impact the county map, they are municipal annexations and thus too numerous and small to list here.
 * December 11, 1941

Dolores County gained territory from Montezuma County.
 * September 1970

The City and County of Broomfield was created from Adams, Boulder, Jefferson, and Weld counties.
 * November 15, 2001

Denver performed its most recent annexation, bringing Colorado to its current state.
 * February 23, 2009