The Straits of Mackinac are the short waterways between the U.S. state of Michigan's Upper and Lower Peninsulas, traversed by the Mackinac Bridge. The main strait is 3+1⁄2 miles wide and has a maximum depth of 295 feet, and connects two of the Great Lakes, Lake Michigan and Lake Huron. Hydrologically, the two connected lakes can be considered one lake, known as Lake Michigan–Huron. Historically, the native Odawa people called the region around the Straits Michilimackinac. The Straits of Mackinac are "whipsawed by currents unlike anywhere else in the Great Lakes".
The three islands forming the eastern edge of Straits of Mackinac include the two populated islands, the Bois Blanc and Mackinac, and one in between them that is uninhabited, the Round island. The Straits of Mackinac are major shipping lanes, providing passage for raw materials and finished goods and connecting, for instance, the iron mines of Minnesota to the steel mills of Gary, Indiana. Before the railroads reached Chicago from the east, most immigrants arrived in the Midwest and Great Plains by ships on the Great Lakes.