El Paso County, with a population of 730,395 in 2020, is the most populous county in Colorado, while San Juan County is the least populous, with a population of 705. Las Animas County, 12369km2 in area, is the most extensive county, while the City and County of Broomfield, 87km2 in area, is the least extensive. The City and County of Denver is the most densely populated Colorado county, with a population density of 4,674 residents per square mile (1,805/km2) as of 2020, while Hinsdale County is the least densely populated county with a population density of 0.71 resident per square mile (0.27/km2).
Mount Elbert, the highest summit of Colorado and the entire Rocky Mountains at an elevation of 4401.2m (14,439.6feet), is located in Lake County. The lowest point in Colorado is where the Arikaree River flows out of Yuma County and into Kansas, at 1011m (3,317feet) elevation. This point, which is the highest low point of any state, is higher than the highest points of 18 states and the District of Columbia.[1] __TOC__
On November 1, 1861, the new Territory of Colorado created 17 original counties: Arapahoe, Boulder, Clear Creek, Costilla, Douglas, El Paso, Fremont, Gilpin, Guadalupe, Huerfano, Jefferson, Lake, Larimer, Park, Pueblo, Summit, and Weld; plus the Cheyenne Reserve.[2] [3] Six days later, the name of Guadelupe County was changed to Conejos County.
On February 9, 1866, the first new county, Las Animas, was created, followed by Saguache in December of that year. Bent County was created in February 1870, followed by Greenwood the following month. On February 2, 1874, Grand County and Elbert County were formed, and on February 10, La Plata, Hinsdale, and Rio Grande counties were created. Greenwood was absorbed into Bent on February 5. The last county to be created under the Colorado Territory name was San Juan County, created three months before statehood.
By the time Colorado became a state on August 1, 1876, it had only 26 counties. In January 1877, Routt and Ouray were formed, followed by Gunnison and Custer counties in March. In February 1879, Chaffee County was created. From February 8–10, 1879, Lake county was renamed Carbonate County. In 1881, Dolores County and Pitkin County were created. In 1883, Montrose, Mesa, Garfield, Eagle, Delta, and San Miguel counties were formed, leaving the total number of counties at 39. The number rose to 40 in 1885 with the creation of Archuleta County on April 14. Washington County and Logan County were both created in 1887. Between February 19 and April 16 in 1889, Morgan, Yuma, Cheyenne, Otero, Rio Blanco, Phillips, Sedgwick, Kiowa, Kit Carson, Lincoln, Prowers, Baca, and Montezuma counties were formed, bringing the total to 55. By 1900, Mineral County and Teller County had been added. On November 15, 1902, Arapahoe County was split into Adams and South Arapahoe Counties, and Denver was consolidated as a city and county from portions of both newly formed counties on December 1, 1902.[4] By 1912, Jackson County, Moffat County, and Crowley County had been created. Alamosa was created in 1913, and in 2001, Broomfield was consolidated as a city and county, bringing the total to 64 counties.
Select the OpenStreetMap link at the right to view the location of these 64 counties.
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For United States Census Bureau population estimates for Colorado counties as of July 1, 2023, see the List of Colorado counties by population. That list ranks the counties by 2023 population and includes population changes since the 2000 United States Census. That list also includes the county websites, links to Colorado Department of Transportation county maps, and the geographic coordinates of the counties.
As of July 1, 2023, El Paso County remains the most populous county in Colorado with a population estimate of 744,215, while Hinsdale County with a 2023 population of 765 is now the least populous. Five of the 64 Colorado counties now have more than 500,000 residents, while 12 counties have fewer than 5,000 residents.
See main article: History of Colorado. The following sortable table lists all the historic counties of the Territory of New Mexico, the Territory of Utah, the Territory of Kansas, and the extralegal Territory of Jefferson[5] that previously existed within the boundaries of the present State of Colorado, as well as the three defunct counties of the Territory of Colorado and the three defunct counties of the State of Colorado.
| Territory or State | scope=col | Date created | scope=col | Date superseded | scope=col | History |
|---|---|---|---|---|---|---|
| scope=row | Taos County | Territory of New Mexico | 1852-01-09 | 1861-02-28 | Originally one of the seven partidos of the Spanish, and later Mexican, province of Santa Fe de Nuevo México. One of the nine original counties created by the Territory of New Mexico in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Great Salt Lake County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Green River County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852, but never organized. Dissolved in 1857, but recreated in 1859. Excluded from the new Territory of Colorado in 1861, and the Territory of Wyoming in 1868. Finally dissolved in 1872. | |
| scope=row | Iron County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Sanpete County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Utah County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Washington County | Territory of Utah | 1852-03-03 | 1861-02-28 | Created in 1852. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Arapahoe County | Territory of Kansas | 1855-08-25 | 1861-01-29 | Created in 1855, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Beaver County | Territory of Utah | 1856-01-05 | 1861-02-28 | Split from Iron and Millard counties in 1856. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Broderick County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Split from Arapahoe County in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | El Paso County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Split from Arapahoe County in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Fremont County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Split from Arapahoe County in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Montana County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Split from Arapahoe County in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Oro County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Split from Arapahoe County in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Peketon County | Territory of Kansas | 1859-02-07 | 1861-01-29 | Created in 1859, but never organized. Reverted to unorganized territory when Kansas joined the Union in 1861. | |
| scope=row | Arapahoe County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Cheyenne County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | El Paso County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Fountain County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Heele County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Jackson County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Jefferson County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Mountain County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | North County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Park County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | St. Vrain County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Saratoga County | Territory of Jefferson | 1859-11-28 | 1861-02-28 | One of the 12 counties created by the extralegal Territory of Jefferson in 1859. | |
| scope=row | Mora County | Territory of New Mexico | 1860-02-01 | 1861-02-28 | Split from Taos County and San Miguel County in 1860. Excluded from the new Territory of Colorado in 1861. | |
| scope=row | Guadalupe County | Territory of Colorado | 1861-11-01 | 1861-11-07 | One of the 17 original counties created by the Territory of Colorado in 1861. The county was renamed Conejos County after only six days. | |
| scope=row | Greenwood County | Territory of Colorado | 1870-02-11 | 1874-02-06 | Created from expropriated Cheyenne and Arapaho tribal land and the eastern portion of Huerfano County in 1870. The county was abolished in 1874 and its territory split between Elbert County and Bent County. | |
| scope=row | Platte County | Territory of Colorado | 1872-02-09 | 1874-02-09 | Created from the eastern portion of Weld County in 1872. The county was abolished in 1874 after organizers failed to secure voter approval. The territory of the county was returned to Weld County. | |
| scope=row | Carbonate County | State of Colorado | 1879-02-08 | 1879-02-10 | Lake County was renamed Carbonate County in 1879. Only two days later, Carbonate County was split into the new Chaffee County and a recreated Lake County. | |
| scope=row | Uncompahgre County | State of Colorado | 1883-02-27 | 1883-03-02 | Ouray County was renamed Uncompahgre County for only four days in 1883. | |
| scope=row | South Arapahoe County | State of Colorado | 1902-11-15 | 1903-04-11 | One of three counties created from Arapahoe County in 1902. The name was changed back to Arapahoe County after five months. |
See main article: List of Colorado county high points.
See also: List of highest U.S. county high points. Of the 64 Colorado counties, 20 counties extend above 14000feet elevation, 32 counties extend above 13000feet, 42 counties extend above 10000feet, and all 64 Colorado counties extend above 4116feet.
See main article: List of highest counties in the United States. Of Colorado's 64 counties, 4 counties have a mean elevation above 11000feet elevation, 22 counties have a mean elevation above 10000feet, 32 counties have a mean elevation above 9000feet, and all 64 counties have a mean elevation above 3880feet.
The following 13 Colorado counties have highest mean elevation of any county in the United States, exceeding even the Denali Borough of Alaska.
| 1 | Lake County | 11702.5feet | Mount Elbert | 14440feet | Arkansas River | 8965feet | 5475feet | |
| 2 | Hinsdale County | 11300feet | Uncompahgre Peak | 14315feet | Lake Fork Gunnison River | 8285feet | 6030feet | |
| 3 | Mineral County | 11116feet | Phoenix Peak | 13902feet | Rio Grande | 8330feet | 5572feet | |
| 4 | San Juan County | 11085feet | Vermilion Peak | 13900feet | Animas River | 8270feet | 5630feet | |
| 5 | Summit County | 10935.5feet | Grays Peak | 14276feet | Blue River | 7595feet | 6681feet | |
| 6 | Alamosa County | 10928.5feet | Blanca Peak | 14351feet | Rio Grande | 7506feet | 6845feet | |
| 7 | Saguache County | 10915feet | Crestone Peak | 14300feet | San Luis Creek | 7530feet | 6770feet | |
| 8 | Costilla County | 10865.5feet | Blanca Peak | 14351feet | Rio Grande | 7380feet | 6971feet | |
| 9 | Park County | 10705.5feet | Mount Lincoln | 14293feet | South Platte River | 7118feet | 7175feet | |
| 10 | Chaffee County | 10661feet | Mount Harvard | 14427feet | Arkansas River | 6895feet | 7532feet | |
| 11 | Clear Creek County | 10608feet | Grays Peak | 14276feet | Clear Creek | 6940feet | 7336feet | |
| 12 | Rio Grande County | 10402feet | Bennett Peak | 13209feet | Rock Creek | 7595feet | 5614feet | |
| 13 | Jackson County | 10353feet | Clark Peak | 12956feet | North Platte River | 7750feet | 5206feet |
1. Costilla County was the first area within the present State of Colorado to be settled by Europeans in 1851.
2. Taos County, created by the Territory of New Mexico in 1852, was the first organized county to extend into the area of the present State of Colorado.
3. Arapahoe County, created by the Territory of Kansas in 1855, was the first county created exclusively within the area of the present State of Colorado.
4. On November 28, 1859, the extralegal Territory of Jefferson created 12 counties:
| Arapahoe County | Denver City | |
| Cheyenne County | ||
| El Paso County | Colorado City | |
| Fountain County | Pueblo | |
| Heele County | La Porte | |
| Jackson County | Boulder City | |
| Jefferson County | Arapahoe City Golden City | |
| Mountain County | Central City | |
| North County | ||
| Park County | Tarryall City | |
| St. Vrain's County | St. Vrain | |
| Saratoga County | Breckinridge |
5. On November 1, 1861, the Territory of Colorado created the 17 original Colorado counties:
| Arapahoe County | Denver City | |
| Boulder County | Boulder City | |
| Clear Creek County | Idaho | |
| Costilla County | San Miguel | |
| Douglas County | Frankstown | |
| El Paso County | Colorado City | |
| Fremont County | Cañon City | |
| Gilpin County | Central City | |
| Guadaloupe County | Guadaloupe | |
| Huerfano County | Autobees Plaza | |
| Jefferson County | Golden City | |
| Lake County | Oro City | |
| Larimer County | La Porte | |
| Park County | Tarryall City | |
| Pueblo County | Pueblo | |
| Summit County | Parkville | |
| Weld County | St. Vrain |
6. Of the 17 original Colorado counties created in 1861, only Gilpin County and Clear Creek County have retained their original boundaries with only minor survey changes.
7. Guadaloupe County was the first Colorado county to be renamed after only six days in 1861.
8. Las Animas County was the first new Colorado county to be created (in 1866) after the original 17 counties.
9. Greenwood County was the longest lived former Colorado county, existing four years from 1870 to 1874.
10. In 1876, San Juan County became the last county created by the Territory of Colorado, bringing the total number of territorial counties to 26.
11. In 1877, Ouray County became the first county created by the new State of Colorado.
12. Carbonate County was the shortest lived former Colorado county, existing only two days in 1879 before being dissolved.
13. The City and County of Broomfield became the newest Colorado county in 2001, bring the total number of counties to 64.
1. El Paso County (88) and the City and County of Denver (93) and are among the 100 most populous counties of the United States.
2. San Juan County (16), Hinsdale County (25), Mineral County (32), Jackson County (55), Kiowa County (59), and Cheyenne County (80) are among the 100 least populous counties of the United States.
3. Jefferson County borders ten adjacent counties, the most of any Colorado county.
4. Delta County and the City and County of Denver each border only three adjacent counties, the fewest of Colorado counties.
5. Weld County has the most incorporated municipalities of any Colorado county with 31.
6. The following nine Colorado counties have no incorporated municipalities other than their county seat:7. Of all 64 Colorado counties, only Conejos County has a county seat that is not an incorporated municipality.
8. The City and County of Denver and the City and County of Broomfield are the only two Colorado counties with enclaves. Arapahoe County, Boulder County, and Jefferson County are the only three Colorado counties with exclaves.