Note: Waterway between Montreal city of Quebec province, Lake Ontario, Canada and New York state, United States; allows passage of vessels between Great Lakes and Atlantic Ocean; massive project was undertaken by the United States and Canada; officially the seaway includes only the 186-mile stretch between Montreal and Lake Ontario and the Welland Canal, connecting Lakes Ontario and Erie; the name is sometimes used to refer to the entire 9.500 miles of the navigable Great Lakes-Saint Lawrence system.
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