Michigan consists of two peninsulas surrounded primarily by four of the Great Lakes and a variety of nearby islands. The Upper Peninsula is bounded on the southwest by Wisconsin, and the Lower Peninsula is bounded on the south by Indiana and Ohio. Both land masses are also separated from the Canadian province of Ontario by waterways of the Great Lakes, and from each other by the Straits of Mackinac. Because its land is largely surrounded by the Great Lakes, which flow into the Saint Lawrence River, Michigan is the only U.S. state whose streams and rivers are almost entirely within the Great Lakes-St. Lawrence watershed.