Columbia County is bordered on the east by the Columbia River, on the south by Multnomah County and Washington County , and on the west by Clatsop County. The southern County line is approximately 30 minutes from Portland, the largest metropolitan area in Oregon. The western County line is approximately 30 minutes from the Pacific coast.

The County's northern and eastern boundaries are outlined by 62 miles of Columbia River shoreline. Columbia County enjoys the longest stretch of the Columbia River in the State of Oregon. The Columbia River is a major route of ocean-going vessels and is a popular fishing ground, as well as a popular boating and windsurfing river.

Facts regarding the early history of Columbia County are few. It is known that a New England trading vessel, the Columbia Rediviva, commanded by Captain Robert Gray arrived in the summer of 1792 with the first Euro-Americans to see the County's timbered shoreline.  In 1805, the explorers Lewis and Clark traveled and camped along the County's Columbia River shoreline.

Carved out of Washington County in 1845, its past was tied to commercial fishing, water transportation and lumber. Industrialization has accelerated in recent years but timber, dairy and horticulture remain important.  Natural gas fields have been identified and are producing.

The County offers the only two marine parks in Oregon: Sand Island on the Columbia River and J.J. Collins Memorial Marine Park on the Multnomah Channel.

Incorporated Cities of Columbia County