There are 9 US Post Offices in Lyon County serving a total of 26,709 residents equating to 2,968 residents per post office. It's estimated that approximately 42,631 packages are handled across the 9 county post offices annually. Lyon County is a county located in the U.S. state of Minnesota. As of the 2010 census, the population was 25,857. Its county seat is Marshall. Lyon County comprises the Marshall, MN Micropolitan Statistical Area."