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.

Interstate 235 (I-235) in Iowa is an auxiliary Interstate Highway that runs just north of downtown Des Moines through the heart of the Des Moines metropolitan area. I-235 runs from the junction of I-35 and I-80 in West Des Moines to the separation of the same two Interstates in Ankeny. The highway is approximately 14 miles (23 km) long.