Mackinac Island is a 4.35 square mile land mass located in Lake Huron in the Straits of Mackinac. The entire island is located within the corporate limits of the City of Mackinac Island. The overwhelming majority of the Island, however, is opened by the state of Michigan. In fact, 82 percent is managed by the Mackinac Island State Park Commission, leaving the city only 18 percent of the island.