There are 6 US Post Offices in Isabella County serving a total of 67,206 residents equating to 11,201 residents per post office. It's estimated that approximately 107,268 packages are handled across the 6 county post offices annually. Isabella County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 70,311. Its county seat is Mt. Pleasant. The area was known as Ojibiway Besse, meaning \"the place of the Chippewa\". It was set off as a county in 1831, and county government organized in 1859. It was named after Queen Isabella I of Castile, based on a suggestion by Henry Rowe Schoolcraft, US Indian Agent and ethnologist. Isabella County comprises the Mount Pleasant, MI Micropolitan Statistical Area in Mid-Michigan, also known as Central Michigan. Within the county is located Isabella Indian Reservation, which has a total area of 217.67 square miles (563.8 km2). It is the major land base of the federally recognized Saginaw Chippewa Tribal Nation. Part of the county seat of Mount Pleasant is located within the reservation."