There are 3 US Post Offices in Brule County serving a total of 5,220 residents equating to 1,740 residents per post office. It's estimated that approximately 8,332 packages are handled across the 3 county post offices annually. Brule County is a county located in the U.S. state of South Dakota. As of the 2010 census, the population was 5,255. Its county seat is Chamberlain. The county was created in 1875 and organized in 1879."