Polk County is located in the U.S. state of Iowa. As of the 2020 census, the population was 492,401. It is Iowa's most populous county, and home to over 15% of the state's residents. The county seat is Des Moines, which is also the capital city of Iowa. Polk County is included in the Des Moines–West Des Moines, IA Metropolitan Statistical Area.

Iowa is a landlocked state in the upper Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Illinois to the east and southeast, Missouri to the south, Nebraska to the west, South Dakota to the northwest, and Minnesota to the north.