There are 1 US Post Offices in Hyde County serving a total of 1,238 residents equating to 1,238 residents per post office. It's estimated that approximately 1,976 packages are handled across the 1 county post offices annually. Hyde County is a county located in the U.S. state of South Dakota. As of the 2010 census, the population was 1,420, making it the fourth-least populous county in South Dakota. Its county seat is Highmore. The county was founded in 1873, as a county of the Dakota Territory, and organized in 1883. It was named for James Hyde, a member of legislature in the 1870s."