Polk County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 87,433. The county seat is Dallas. The county is named for James Knox Polk, the 11th president of the United States.

Salem is the capital city of the U.S. state of Oregon, and the county seat of Marion County. It is located in the center of the Willamette Valley alongside the Willamette River, which runs north through the city. The river forms the boundary between Marion and Polk counties, and the city neighborhood of West Salem is in Polk County. Salem was founded in 1842, became the capital of the Oregon Territory in 1851, and was incorporated in 1857.