Polk County Courthouse. Polk County. – Gary Halvorson, Oregon State Archives, CC BY 4.0 – Wikimedia Commons Polk County is located in Oregon. About 79,391 people live here. Between 2010 and 2020, the population grew from 75,403 to 87,433. The area covers about 1,927.0 square kilometers. The region is divided into 4 Municipalities. The region was founded in 1845. The name originates from James K. Polk (President of the United States from 1845 to 1849) Polk County is county in Oregon, United States. More information at www.co.polk.or.us.