St. Marys River (Michigan–Ontario) St. Marys River (Michigan–Ontario) The St. Marys River (), sometimes written as the St. Mary's River, drains Lake Superior, starting at the end of Whitefish Bay and flowing southeast into Lake Huron, with a fall of . For its entire length it is an international border, separating Michigan in the United States from Ontario, Canada. The twin cities of Sault Ste. Marie, Ontario, and Sault Ste. Marie, Michigan are connected across the St. Marys River by the Sault Ste. Marie International Bridge. The St. Marys Rapids are just below the river's exit from Lake Superior and can be bypassed by
Sault Ste. Marie, Michigan Sault Ste. Marie, Michigan Sault Ste. Marie is a city in, and the county seat of, Chippewa County in the U.S. state of Michigan. It is situated on the northeastern end of Michigan's Upper Peninsula, on the Canada–US border, and separated from its twin city of Sault Ste. Marie, Ontario, by the St. Marys River. The city is relatively isolated from other communities in Michigan and is 346 miles from Detroit. The population was 14,144 at the 2010 census, making it the second-most populous city in the Upper Peninsula. By contrast, the Canadian Sault Ste. Marie is much larger, with