There are 10 US Post Offices in Mackinac County serving a total of 10,193 residents equating to 1,019 residents per post office. It's estimated that approximately 16,269 packages are handled across the 10 county post offices annually. Mackinac County is a county in the Upper Peninsula of the U.S. state of Michigan. As of the 2010 census, the population was 11,113. The county seat is St. Ignace. Formerly known as Michilimackinac County, in 1818 it was one of the first counties of the Michigan Territory, as it had long been a center of French and British colonial fur trading, a Catholic church and Protestant mission, and associated settlement. The county's name is believed to be shortened from the French term \"Michilimackinac,\" which referred to the Straits of Mackinac area as well as the French settlement at the tip of the lower peninsula."