There are 8 US Post Offices in Williamsburg County serving a total of 43,054 residents equating to 5,382 residents per post office. It's estimated that approximately 68,719 packages are handled across the 8 county post offices annually. Williamsburg County is a county located in the U.S. state of South Carolina. As of the 2010 census its population was 34,423. The county seat is Kingstree. After a previous incarnation of Williamsburg County, the current county was created in 1804."