There are 6 US Post Offices in Rock County serving a total of 9,542 residents equating to 1,590 residents per post office. It's estimated that approximately 15,230 packages are handled across the 6 county post offices annually. Rock County is a county located in the U.S. state of Minnesota, in the far southwestern corner of the state. As of the 2010 census, the population was 9,687. Its county seat is Luverne. The county was formed in 1857 and organized in 1870. Rock County was named for the rocky soil."