There are 10 US Post Offices in Colleton County serving a total of 36,589 residents equating to 3,659 residents per post office. It's estimated that approximately 58,400 packages are handled across the 10 county post offices annually. Colleton County is a county located in the Lowcountry region of the U.S. state of South Carolina. As of the 2010 census, its population was 38,892. Its county seat is Walterboro. The county is named after Sir John Colleton, 1st Baronet, one of the eight Lords Proprietor of the Province of Carolina. After two previous incarnations, the current Colleton County was created in 1800."