The Upper Peninsula of Michigan is the northern and more elevated of the two major landmasses that comprise the U.S. state of Michigan; it is separated from the Lower Peninsula by the Straits of Mackinac. It is bounded primarily by Lake Superior to the north, separated from the Canadian province of Ontario at the east end by the St. Marys River, and flanked by Lake Huron and Lake Michigan along much of its south. Although the peninsula as a geographic feature extends into the state of Wisconsin, the state boundary follows the Montreal and Menominee rivers with a line connecting them.