
Columbia County
- State:
- Washington
- County Seat:
- Dayton
Columbia County's estimated 2025 population is 4,107 with a growth rate of 0.66% in the past year according to the most recent United States census data. Columbia County is the 38th largest county in Washington. The 2010 population was 4,094 and has seen a growth of 0.32% since that time.