Oregon City is the county seat of Clackamas County, Oregon. It is located on the Willamette River near the southern limits of the Portland metropolitan area. Astoria is a port city and the county seat of Clatsop County, Oregon, located near the mouth of the Columbia River. Portland is the largest and most populous city in the U.S. state of Oregon and the seat of Multnomah County. Eugene is a city in the U.S. state of Oregon, located at the southern end of the Willamette Valley. Salem is the capital of the U.S. state of Oregon, and the county seat of Marion County.