There are 64 counties in Colorado. The most populous county in Colorado in 2019 is Denver County, home of Denver, with a population of 704,621. This represents significant population growth of 16.81% since the 2010 census. Colorado is home to several other counties exceeding 500,000 residents including El Paso County (699,232), Arapahoe County (643,052), Jefferson County (574,613), and Adams County (503,167). All of these counties have experienced population growth of at least 7% but not exceeding Denver County's growth.
The smallest county in Colorado in terms of population is San Juan County with just 715 people, up 0.99% from the last census. There are two other counties in Colorado with populations under 800: Mineral County (766) and Hinsdale County (794). Colorado has a total of 26 counties under 10,000 residents. Other small Colorado counties include Kiowa County (1,376), Jackson County (1,385), Cheyenne County (1,845), Dolores County (2,067), and Sedgwick County (2,344). The most significant growth among these counties was Mineral County at 8.81%. Hinsdale County experienced the most dramatic decline with a growth rate of -5.92%.
Broomsfield County, Colorado experienced the most significant population growth in the state since the census, growing by 21.57%. Other counties with rapid growth rates include Weld County (19.85%), Douglas County (16.85%), Denver County (16.81%), and Larimer County (14.50%). The county that has experienced the most extreme negative growth is Kit Carson County with a growth rate of -13.38% which has brought its population down to 7,158.