St. Marys River serves as vital US-Canada maritime border

The St. Marys River, which serves as the international border between Michigan and Ontario, remains a vital corridor for both commerce and recreation. The area is home to the Soo Locks, which allow Great Lakes freighters to navigate the elevation drop between Lake Superior and Lake Huron.

Under international law and agreements between the United States and Canada, recreational boaters may cross into Canadian waters within the Great Lakes, St. Marys River, Detroit River, and Lake St. Clair, provided they do not anchor, dock, or touch land. The economies of the Great Lakes region maintain a close relationship through these shared waterways.