The Detroit River, 52 km long, flows south from Lake ST CLAIR to the west end of Lake ERIE, forming part of the boundary between Ontario and Michigan. Detroit, Michigan, and WINDSOR, Ontario, dominate its shores. Part of the ST LAWRENCE SEAWAY, it is heavily used by commercial traffic. The largest islands are Michigan's Belle Isle, a park, and Grosse Ile, site of an American naval base and Ontario's Fighting Island. The name comes from the French word for strait or narrows.