 There is one more interchange along the freeway before I-75 ascends the approaches to the Mackinac Bridge.The Mackinac Bridge carries I-75 across the Straits of Mackinac that separate Michigan's Upper and Lower peninsulas; the straits also form the connection between Lakes Michigan and Huron.The structure, unlike the rest of the state highways in Michigan like I-75, is under the maintenance and control of the Mackinac Bridge Authority (MBA).