There are currently 64 counties in the U.S. State of Colorado but before Colorado became a U.S. state in 1876, it had only 26 counties. The number rose to 40 in 1885 after the creation of Archuleta County and eventually to 64 counties in 2001 when Broomfield was consolidated as a city and county.
These Colorado counties are important units of government in the state because there’re no townships or other minor civil divisions.
Out of these 64 counties, two (Broomfield and Denver) have consolidated city and county governments. Each county in Colorado has its own character and sense of identity.
Here is a list of all the counties in Colorado, their FIPS code, year formed, and population.
Table of Contents
List of all Colorado Counties
| County Name | County Seat | FIPS Code | Year Formed | Population as of 2019 |
| Adams County | Brighton | 001 | 1902 | 517,421 |
| Alamosa County | Alamosa | 003 | 1913 | 16,107 |
| Arapahoe County | Littleton | 005 | 1861 | 656,590 |
| Archuleta County | Pagosa Springs | 007 | 1885 | 13,253 |
| Baca County | Springfield | 009 | 1889 | 3,561 |
| Bent County | Las Animas | 011 | 1870 | 5,787 |
| Boulder County | Boulder | 013 | 1861 | 326,196 |
| Broomfield County | Broomfield | 014 | 2001 | 67,886 |
| Chaffee County | Salida | 015 | 1879 | 19,557 |
| Cheyenne County | Cheyenne Wells | 017 | 1889 | 2,026 |
| Clear Creek County | Georgetown | 019 | 1861 | 9,700 |
| Conejos County | Conejos | 021 | 1861 | 8,128 |
| Costilla County | San Luis | 023 | 1861 | 3,745 |
| Crowley County | Ordway | 025 | 1911 | 5,754 |
| Custer County | Westcliffe | 027 | 1877 | 4,776 |
| Delta County | Delta | 029 | 1883 | 30,565 |
| Denver County | Denver | 031 | 1902 | 735,538 |
| Dolores County | Dove Creek | 033 | 1881 | 1,857 |
| Douglas County | Castle Rock | 035 | 1861 | 351,154 |
| Eagle County | Eagle | 037 | 1883 | 55,127 |
| El Paso County | Colorado Springs | 041 | 1861 | 720,403 |
| Elbert County | Kiowa | 039 | 1874 | 26,729 |
| Fremont County | Cañon City | 043 | 1861 | 47,839 |
| Garfield County | Glenwood Springs | 045 | 1883 | 60,061 |
| Gilpin County | Central City | 047 | 1861 | 6,243 |
| Grand County | Hot Sulphur Springs | 049 | 1874 | 15,303 |
| Gunnison County | Gunnison | 051 | 1877 | 16,802 |
| Hinsdale County | Lake City | 053 | 1874 | 857 |
| Huerfano County | Walsenburg | 055 | 1861 | 6,679 |
| Jackson County | Walden | 057 | 1909 | 1,261 |
| Jefferson County | Golden | 059 | 1861 | 582,881 |
| Kiowa County | Eads | 061 | 1889 | 1,489 |
| Kit Carson County | Burlington | 063 | 1889 | 7,447 |
| La Plata County | Durango | 067 | 1874 | 56,221 |
| Lake County | Leadville | 065 | 1861 | 7,751 |
| Larimer County | Fort Collins | 069 | 1861 | 356,899 |
| Las Animas County | Trinidad | 071 | 1866 | 14,266 |
| Lincoln County | Hugo | 073 | 1889 | 5,585 |
| Logan County | Sterling | 075 | 1887 | 22,409 |
| Mesa County | Grand Junction | 077 | 1883 | 154,210 |
| Mineral County | Creede | 079 | 1893 | 824 |
| Moffat County | Craig | 081 | 1911 | 13,283 |
| Montezuma County | Cortez | 083 | 1889 | 26,031 |
| Montrose County | Montrose | 085 | 1883 | 42,758 |
| Morgan County | Fort Morgan | 087 | 1889 | 29,068 |
| Otero County | La Junta | 089 | 1889 | 18,282 |
| Ouray County | Ouray | 091 | 1877 | 4,952 |
| Park County | Fairplay | 093 | 1861 | 18,845 |
| Phillips County | Holyoke | 095 | 1889 | 4,290 |
| Pitkin County | Aspen | 097 | 1881 | 17,767 |
| Prowers County | Lamar | 099 | 1889 | 12,022 |
| Pueblo County | Pueblo | 101 | 1861 | 168,424 |
| Rio Blanco County | Meeker | 103 | 1889 | 6,384 |
| Rio Grande County | Del Norte | 105 | 1874 | 11,305 |
| Routt County | Steamboat Springs | 107 | 1877 | 25,638 |
| Saguache County | Saguache | 109 | 1866 | 6,592 |
| San Juan County | Silverton | 111 | 1876 | 589 |
| San Miguel County | Telluride | 113 | 1883 | 8,049 |
| Sedgwick County | Julesburg | 115 | 1889 | 2,322 |
| Summit County | Breckenridge | 117 | 1861 | 31,011 |
| Teller County | Cripple Creek | 119 | 1899 | 25,388 |
| Washington County | Akron | 121 | 1887 | 4,868 |
| Weld County | Greeley | 123 | 1861 | 324,492 |
| Yuma County | Wray | 125 | 1889 | 10,003 |
10 Most Populous Colorado Counties
1. Denver County
Denver is a consolidated city and a county government. It was established in 1858 as a mining town during the heady days of the Pike’s Peak Gold Rush.
Denver is the capital and the most populous city in Colorado with an estimated population of 735,538. Denver is U.S.’s 19th most populous city and the 5th most populous state capital.
2. El Paso County
El Paso County was founded on November 1, 1861. Its largest city and county seat is Colorado Springs which is the second-most populous city in Colorado.
According to the U.S. Census Bureau, El Paso County’s population as of 2019 was estimated to be 720,403, making it the second-most populous county in Colorado.
El Paso County is home to numerous military sites such as the United States Air Force Academy, Fort Carson Army, North American Aerospace Defense Command (NORAD), Schriever Air Force Base, and Peterson Air Force Base.
3. Arapahoe County
Arapahoe County is the third-most populous county in Colorado with an estimated population of 656,590. It was founded in 1861 and its county seat is Littleton and its largest city is Aurora.
Arapahoe County was named for the Arapaho Native American tribe, who once lived in the region.
4. Jefferson County
Jefferson County was established on November 1, 1861. It is the fourth most populous county in Colorado with an estimated population of 582,881. Its county seat is Golden and its largest city is Lakewood.
Jefferson County’s slogan is the “Gateway to the Rocky Mountains” and it is commonly nicknamed JeffCo.
5. Adams County
Adams County was founded April 15, 1901, and named for Alva Adams an American politician. It is the fifth most populous county in Colorado with an estimated population of 517,421.
Its county seat is Brighton and its largest city is Thornton.
6. Larimer County
Larimer County was founded November 1, 1861, and named for William Larimer, Jr, the founder of Denver. Its county seat and largest city is Fort Collins.
Larimer County is the sixth most populous county in Colorado with an estimated population of 356,899.
7. Douglas County
As of 2019, Douglas County’s population was estimated to be 351,154, making it the seventh most populous county in Colorado.
The largest community in Douglas County is Highlands Ranch and its county seat is Castle Rock. Douglas County was created in 1861 and was named for Stephen A. Douglas.
8. Boulder County
Boulder County was founded in 1861 and named for Boulder City and Boulder Creek. Its largest city and county seat is Boulder.
As of 2019, its population was estimated to be 326,196 making it the eighth most populous county in Colorado.
9. Weld County
Weld County estimated population as of 2019 was 324,492, making it the ninth most populous county in Colorado. It is also the 3rd largest county in Colorado by area covering 4,017 square miles.
Weld County is Colorado’s largest cattle producer, accounting for about half of the state’s total cattle inventory.
It is also one of the largest providers of grains and sugar beets making it one of the richest agricultural counties in the United States.
10. Pueblo County
Pueblo County had a population of 168,424 in 2019, making it the tenth most populous county in Colorado. The county was founded in 1861 and was named for the historic City of Pueblo.
Its county seat and largest city is Pueblo.
