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.HistoryCass County was created on September 1, 1851 by the legislature of the Minnesota Territory. It was not formally organized until 1897. Cass County was formed from portions of Dakota, Mahkatah, Pembina and Wahnata Counties. The county was named in honor of Lewis Cass. In turn, before formal organization, land from Cass County was split off to form other of the surrounding counties.