Lawrence is the only outflow to the sea from the Great Lakes. For about 115 miles after leaving the lake, the St. Lawrence forms the boundary between the U.S and Canada, making it the second longest river in Canada and 700 miles long.
The Saint Lawrence Seaway includes the Great Lakes, which make up about half of the total length. It is very important economically, its system of canals, locks, deepened channels and waterways are the most important in North America, large sea-going ships can reach Quebec and Montreal, and the seaway allows smaller ships to call at inland lake ports such as Toronto, Hamilton, Buffalo, Detroit, Chicago, Milwaukee and Duluth Superior on the Great Lakes.
On its way to the Atlantic Ocean from Lake Ontario, the Saint Lawrence falls 75 metres. Nearly all of this drop is made in the short and fairly short stretch before the river reaches Montreal 168 miles downstream. Therefore, the water flows extremely fast in this stretch. To avoid these rapids, canals and locks were built to allow ships to use the river system above Montreal. .
However, the canals were too shallow at 4 metres, and the locks were too small to take big ships. Canada and the United States set to work in the 1950s to build new canals and larger locks. At the same time they produced dams to provide water for electric power stations. The power stations at the Long Sault Rapids and at the Beauharnios alone provide as much electricity as is used by the city of New York, which I think is substantial achievement.
The St. Lawrence Seaway was completed in 1959, when the opening ceremonies were held in the presence of Queen Elizabeth II and President Eisenhower. Ships using the seaway pay a toll towards maintenance and operating costs. The seaway cannot be used in winter as the Great Lakes and river ports often freeze at this time, and the Gulf of St. Lawrence is often blocked by ice sometimes until mid April.
