There are 5 US Post Offices in Polk County serving a total of 20,837 residents equating to 4,167 residents per post office. It's estimated that approximately 33,258 packages are handled across the 5 county post offices annually. Polk County is a county located in the U.S. state of North Carolina. As of the 2010 census, the population was 20,510. Its county seat is Columbus. The county was formed in 1855 from parts of Henderson County and Rutherford County. It was named for William Polk, a colonel in the American Revolutionary War."