The Chinook and Clatskanie Native Americans inhabited this region for centuries prior to the arrival of Robert Gray, captain of the ship Columbia Rediviva, in 1792. The Lewis and Clark Expedition, traveled and camped along the Columbia River shore in the area later known as Columbia County in late 1805 and on their return journey in early 1806.

Columbia County, was created in 1854 from the northern half of Washington County.The county was named in 1854 (prior to statehood) for the Columbia River, which forms its eastern and northern borders. As of 2000, the population is 43,560.