There are 6 US Post Offices in Lawrence County serving a total of 22,854 residents equating to 3,809 residents per post office. It's estimated that approximately 36,478 packages are handled across the 6 county post offices annually. Lawrence County is a county located in the U.S. state of South Dakota. As of the 2010 census, the population was 24,097. Its county seat is Deadwood. Lawrence County is coextensive with the Spearfish, SD Micropolitan Statistical Area, which is also included in the Rapid City-Spearfish, SD Combined Statistical Area."