There are 5 US Post Offices in Calhoun County serving a total of 13,275 residents equating to 2,655 residents per post office. It's estimated that approximately 21,188 packages are handled across the 5 county post offices annually. Calhoun County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 14,962. Its county seat is Pittsboro. The county is named after John C. Calhoun, the U.S. Vice President and U.S. Senator from South Carolina."