The primary purpose of the St. Lawrence Seaway, built in the 1950s, was to improve shipping access between the U.S. and Canada.

The St. Lawrence Seaway opened in 1959, was designed to enhance trade and shipping access between the U.S. and Canada. Before its construction, the Great Lakes were inaccessible to large oceangoing vessels due to their shallow depth. The Seaway, a system of locks, canals, and channels, made it possible for these ships to travel from the Atlantic Ocean to the Great Lakes. This development significantly boosted commerce, especially for industries in the Midwest and Canada, by facilitating the movement of bulk goods like iron ore, coal, and grain, strengthening the economies of both nations.