- Columbia County, Washington has 868.6 square miles of land area and is the 31st largest county in Washington by total area. Columbia County, Washington is bordered by Walla Walla County, Washington, Franklin County, Washington, Garfield County, Washington, Wallowa County, Oregon, Umatilla County, Oregon, and Whitman County, Washington.
- Columbia County, Oregon (data.census.gov)
Columbia County, Oregon has 658.7 square miles of land area and is the 34th largest county in Oregon by total area. Columbia County, Oregon is bordered by Cowlitz County, Washington, Washington County, Oregon, Multnomah County, Oregon, Clark County, Washington, Tillamook County, Oregon, Clatsop County, Oregon, and Wahkiakum County, Washington.