
Douglas County
- State:
- Colorado
- County Seat:
- Castle Rock
Douglas County's estimated 2025 population is 399,844 with a growth rate of 2.03% in the past year according to the most recent United States census data. Douglas County is the 6th largest county in Colorado. The 2010 population was 287,011 and has seen a growth of 39.31% since that time.