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 on the lower (east) side of the Soo Locks. The United States Postal Service operates a "Marine Post Office", situated within the locks, to service ships as they pass through. The city is located at Latitude: 46.49 N, Longitude: -84.35 W. According to the United States Census Bureau, the city has a total area of , of which is land and is water. Under the Köppen climate classification, Sault Ste. Marie has a humid continental climate ("Dfb") with cold, snowy winters and warm summers. Sault Ste. Marie is one of the snowiest places in Michigan, receiving an average of of