colorado counties

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.

List of all Colorado Counties

County NameCounty SeatFIPS CodeYear FormedPopulation as of 2019
Adams CountyBrighton0011902517,421
Alamosa CountyAlamosa003191316,107
Arapahoe CountyLittleton0051861656,590
Archuleta CountyPagosa Springs007188513,253
Baca CountySpringfield00918893,561
Bent CountyLas Animas01118705,787
Boulder CountyBoulder0131861326,196
Broomfield CountyBroomfield014200167,886
Chaffee CountySalida015187919,557
Cheyenne CountyCheyenne Wells01718892,026
Clear Creek CountyGeorgetown01918619,700
Conejos CountyConejos02118618,128
Costilla CountySan Luis02318613,745
Crowley CountyOrdway02519115,754
Custer CountyWestcliffe02718774,776
Delta CountyDelta029188330,565
Denver CountyDenver0311902735,538
Dolores CountyDove Creek03318811,857
Douglas CountyCastle Rock0351861351,154
Eagle CountyEagle037188355,127
El Paso CountyColorado Springs0411861720,403
Elbert CountyKiowa039187426,729
Fremont CountyCañon City043186147,839
Garfield CountyGlenwood Springs045188360,061
Gilpin CountyCentral City04718616,243
Grand CountyHot Sulphur Springs049187415,303
Gunnison CountyGunnison051187716,802
Hinsdale CountyLake City0531874857
Huerfano CountyWalsenburg05518616,679
Jackson CountyWalden05719091,261
Jefferson CountyGolden0591861582,881
Kiowa CountyEads06118891,489
Kit Carson CountyBurlington06318897,447
La Plata CountyDurango067187456,221
Lake CountyLeadville06518617,751
Larimer CountyFort Collins0691861356,899
Las Animas CountyTrinidad071186614,266
Lincoln CountyHugo07318895,585
Logan CountySterling075188722,409
Mesa CountyGrand Junction0771883154,210
Mineral CountyCreede0791893824
Moffat CountyCraig081191113,283
Montezuma CountyCortez083188926,031
Montrose CountyMontrose085188342,758
Morgan CountyFort Morgan087188929,068
Otero CountyLa Junta089188918,282
Ouray CountyOuray09118774,952
Park CountyFairplay093186118,845
Phillips CountyHolyoke09518894,290
Pitkin CountyAspen097188117,767
Prowers CountyLamar099188912,022
Pueblo CountyPueblo1011861168,424
Rio Blanco CountyMeeker10318896,384
Rio Grande CountyDel Norte105187411,305
Routt CountySteamboat Springs107187725,638
Saguache CountySaguache10918666,592
San Juan CountySilverton1111876589
San Miguel CountyTelluride11318838,049
Sedgwick CountyJulesburg11518892,322
Summit CountyBreckenridge117186131,011
Teller CountyCripple Creek119189925,388
Washington CountyAkron12118874,868
Weld CountyGreeley1231861324,492
Yuma CountyWray125188910,003

10 Most Populous Colorado Counties

1. Denver County  

colorado counties

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 

colorado counties

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

colorado counties

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 

colorado counties

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  

colorado counties

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  

colorado counties

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  

colorado counties

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  

colorado counties

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.  

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