There are 11 US Post Offices in Cass County serving a total of 26,880 residents equating to 2,444 residents per post office. It's estimated that approximately 42,903 packages are handled across the 11 county post offices annually. Cass County is a county located in the U.S. state of Minnesota. As of the 2010 census, the population was 28,567. Its county seat is Walker. The county was formed in 1851 and organized in 1897. Cass County is included in the Brainerd, MN Micropolitan Statistical Area. A substantial portion of the Leech Lake Indian Reservation is in the county."