There are 8 US Post Offices in Dorchester County serving a total of 134,266 residents equating to 16,783 residents per post office. It's estimated that approximately 214,304 packages are handled across the 8 county post offices annually. Dorchester County is a county located in the U.S. state of South Carolina. As of the 2010 census, the population was 136,555. Its county seat is St. George. Dorchester County is included in the Charleston-North Charleston, SC Metropolitan Statistical Area."