STS040-077-044 The Great Lakes, U.S.A. and Canada June 1991 Portions of all five Great Lakes, the largest combined body of fresh water in the world [covering an area of 95 000 square miles (246 050 square kilometers)], can be seen in this high-oblique, northeast-looking photograph. Lake Michigan alone covers an area of 22 300 square miles (57 755 square kilometers). This lake can be seen in the center of the photograph, with Chicago on its southwestern shore. The Great Lakes were formed about 12 000 years ago at the end of the ice age, when glacier-carved lake basins were filled with meltwater. The lakes are interconnected by straits, short rivers, and canals. Water from the Great Lakes exits at the eastern end of Lake Ontario into the Saint Lawrence River, which flows on eastward into the Atlantic Ocean.