There are 6 US Post Offices in Osceola County serving a total of 22,849 residents equating to 3,808 residents per post office. It's estimated that approximately 36,470 packages are handled across the 6 county post offices annually. Osceola County is a county located in the U.S. state of Michigan. At the 2010 census, the population was 23,528. The county seat is Reed City. Osceola County was set off on April 1, 1840, named \"Unwattin County\", after an Ottawa leader. The name was changed March 8, 1843, to Osceola, after the Seminole leader. It was initially attached for administrative purposes to Ottawa County. In 1855, it was attached to Mason County; in 1857, to Newaygo County; and in 1859, to Mecosta County. Separate county government was organized in 1869 with Hersey as the county seat. Reed City became the county seat in 1927."