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How does the St. Lawrence Seaway support international trade for Great Lakes cities?

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Map showing the St. Lawrence hydrographic system and the five main sectors of the St. Lawrence Seaway project, stretching from Lake Ontario near Kingston through various locks, canals, and dams along the Canada-United States border to Montreal. The map highlights key locations such as the Thousand Islands, International Rapids, Lake St. Francis, Soulanges, and Lachine sections, with detailed labeling of major locks, canals, and power dams. Cross sections of the lock and canal system are depicted — St. Lawrence Seaway The St. Lawrence hydrographic system, with the five main sectors of the St. Lawrence Seaway project.

The St. Lawrence Seaway supports international trade for Great Lakes cities by providing a continuous, deep-draft navigable waterway that connects the industrial and agricultural heartlands of North America to the Atlantic Ocean. By clearing a throughway and utilizing a system of locks and canals, the seaway allows large vessels to bypass navigational hazards, effectively turning the Great Lakes into a vast inland sea for global commerce.123

Key ways the seaway facilitates this trade include:

Bulk Commodity Transport: The system moves approximately 140 million metric tons of cargo annually. It enables the cost-effective export of grain from the American Midwest and Canadian prairies to world markets.24
Industrial Supply Chains: It serves as a vital route for moving iron ore and coal to support steel mills and power plants in the United States and Canada.24
Vessel Efficiency: Specialized ships known as lakers are designed to maximize the dimensions of the seaway locks, facilitating efficient two-way trade.24
Global Access: Beyond bulk goods, the route allows vessels from many nations to deliver or pick up general cargoes directly at Great Lakes ports.24