This seaway has a total length of 2,342 miles (3,796 km) between the Atlantic Ocean and its western terminus in Lake Superior. It allows major oceanic vessels to reach the Great Lakes, thus enabling ports as far inland as the west side of Lake Superior to serve as international ports.
The seaway was completed in 1959, although Canada and the United States began to anticipate such a waterway project in the last years of the 19th century.