There are 9 US Post Offices in Polk County serving a total of 31,451 residents equating to 3,495 residents per post office. It's estimated that approximately 50,199 packages are handled across the 9 county post offices annually. Polk County is a county located in the southwestern portion of the U.S. state of Missouri. As of the 2010 census, the population was 31,137. Its county seat is Bolivar. The county was founded January 5, 1835, and named for Ezekiel Polk. Polk County is part of the Springfield, MO Metropolitan Statistical Area."