Polk City is a city in Polk County, Iowa, United States. The population was 5543 in the 2020 census, an increase from 2,344 in 2000. It is part o…Polk City is a city in Polk County, Iowa, United States. The population was 5543 in the 2020 census, an increase from 2,344 in 2000. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area.