The St. Lawrence Seaway primarily handles the shipment of grain, particularly from the Midwest U.S. and Canada to global markets.

The Seaway provides a vital waterway for transporting bulk agricultural commodities like corn, wheat, and soybeans, which are major exports for both the U.S. and Canada. These grains are often loaded onto large ships for export to Europe, Asia, and other parts of the world. In addition to grain, the St. Lawrence Seaway also handles other bulk commodities, including coal and iron ore, but grain remains one of its most significant cargoes. The Seaway's role in global food trade is critical for both economies.