The Saint Lawrence Seaway is a series of canals that permits ocean-going vessels to reach the Great Lakes from the Atlantic Ocean. It begins at the port of Montreal, where the South Shore Canal (St-Lambert and Ste-Catherine locks) passes the Lachine Rapids. West of the Island of Montreal and Lac Saint-Louis, the Beauharnois canal and locks pass the Beauharnois hydroelectric dam.
The seaway then leaves Quebec through Lac Saint-François and the Akwesasne Mohawk First Nation, and passes through New York State and Ontario. In New York, the Wiley-Dondero Canal (Snell and Eisenhower locks) passes the Moses-Saunders power dam, and the short Iroquois lock passes the Iroquois water level control structure.