There are 3 US Post Offices in Calhoun County serving a total of 4,158 residents equating to 1,386 residents per post office. It's estimated that approximately 6,637 packages are handled across the 3 county post offices annually. Calhoun County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 5,368, making it the least populous county in Arkansas. The county seat is Hampton. Calhoun County is Arkansas's 55th county, formed on December 6, 1850, and named for John C. Calhoun, a Vice President of the United States. The county is part of the Camden, AR Micropolitan Statistical Area."