Columbia County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 3,952, making it the second-least populous county in Washington. The county seat and largest city is Dayton. The county was created out of Walla Walla County on November 11, 1875, and is named after the Columbia River (which does not flow through the county). Columbia County is included in the Walla Walla, WA Metropolitan Statistical Area.
Geography
According to the United States Census Bureau, the county has a total area of , of which is land and (0.6%) is water. It is part of the Palouse, a wide and rolling prairie-like region of the middle Columbia basin.
Geographic features
- Snake River
- Blue Mountains
- Touchet River
- Tucannon River
Major highways
- 20px U.S. Route 12
Adjacent counties
- Whitman County - north
- Garfield County - east
- Wallowa County, Oregon - southeast
- Umatilla County, Oregon - southwest
- Walla Walla County - west
- Franklin County - northwest
National protected area
- Umatilla National Forest (part)