Saint Marys River

Saint Marys River, river on the border between Ontario and Michigan that drains Lake Superior, then flows less than 70 mi (110 km) to empty into Lake Huron. The river is part of the St. Lawrence and Great Lakes Waterway, which links the Great Lakes with the Atlantic Ocean. The St. Marys Rapids near Lake Huron make the river impassable for large boats; these are diverted to the Sault Ste. Marie (or Soo) Canals. Saint Marys River is a source of hydroelectric power.