The largest county in Colorado by square mileage is Las Animas County, with a total size of 4,773.27 square miles. Ranked by population, the largest Colorado county is El Paso County, with a population of 622,263 people as of the 2010 census.
The city and county of Denver is the second largest county by population, home to 600,158 people as of the 2010 U.S. census. It is followed by Arapahoe County, with 572,003 people; Jefferson County, with 534,543 people; and Adams county, with 441,603 people. The smallest county by population is San Juan County, with a population of 699. The smallest county by area is the city and county of Broomfield, with a square footage of 33.57.