There are 7 US Post Offices in Calhoun County serving a total of 6,745 residents equating to 964 residents per post office. It's estimated that approximately 10,766 packages are handled across the 7 county post offices annually. Calhoun County is a county located in the U.S. state of West Virginia. As of the 2010 census, the population was 7,627. Its county seat is Grantsville. The county was founded in 1856 and is named for South Carolina politician John C. Calhoun."