In contrast, so far since it opened in 1959, the history of the world’s longest artificial seaway has been peaceful. Ocean vessels can enter the St. Lawrence Seaway through the Gulf of St. Lawrence. Next they can travel up the river to Lake Ontario, passing through the Welland Canal into Lakes Erie, Huron and Michigan, and then through the locks at Sault Ste. Marie into Lake Superior. At this point they have climbed more than 600 feet (183 meters) since entering the Seaway, the equivalent of a 60-story building! They can then cross to Duluth at the western tip of Lake Superior, 2,342 miles (3,768 kilometers) from the Atlantic Ocean. Also, in contrast with the Panama Canal, the Seaway’s traffic has been increasing. Already there is talk of adding to its capacity before the mid-1980’s.

Also, the St. Lawrence Seaway has led to expanded industrial activity along the Great Lakes and this has accelerated pollution of their waters.