There are 7 US Post Offices in Polk County serving a total of 20,851 residents equating to 2,979 residents per post office. It's estimated that approximately 33,281 packages are handled across the 7 county post offices annually. Polk County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 20,662. The county seat is Mena. Polk County is Arkansas's 48th county, formed on November 30, 1844, and named for James Polk, President of the United States. It is an alcohol prohibition or dry county. Polk County is the setting for Stephen Hunter's fictional Bob Lee Swagger series, the most notable being Black Light, as well as the place where Joel B Reed's fictional character, Jazz Phillips, of the Jazz Phillips mystery series, grew up."