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St. Lawrence Seaway

Officially, the St. Lawrence Seaway refers to a system of channels, canals and locks on and along the St. Lawrence River that allows ocean-going vessels to sail from the Atlantic Ocean to Lake Ontario. Unofficially, it refers to the entire Great Lakes-St. Lawrence River Seaway system that extends the system of channels, canals and locks all the way through the Great Lakes to Duluth, Minnesota, a total distance of 2,342 miles.

map of the Great Lakes St. Lawrence River Seaway


French explorer Jacques Cartier discovered the St. Lawrence River in 1535. He hoped the river would open into the Northwest Passage, but he was stopped by the rapids at present-day Montreal. French fur traders and missionaries built a shallow canal with a wooden lock around these rapids in 1700. The Canadians continued to build canals, and by 1903 they had completed a navigable channel 14 feet deep from the Atlantic Ocean to Lake Erie. In 1823, the United States began to improve the channels between the Great Lakes. By 1914, the United States had provided channels 25 feet deep from Lake Superior to Lake Erie.

The improved channels became outmoded as the amount of ship traffic and ship sizes increased. By the 1890's, citizens of both Canada and the United States were urging the cooperative development of the St. Lawrence River system resources. A joint commission was created in 1911, with authority over the boundary waters of the United States and Canada. In the 1920's, that commission recommended that a joint power-and-navigation project be undertaken.

A treaty was signed by representatives of both nations in 1932. It provided for the construction of a waterway 27 feet deep from the Atlantic Ocean to the head of Lake Superior. It also provided for development of hydroelectric power in the International Rapids section of the St. Lawrence River. Power and costs were to be shared equally by the two nations. U.S. railroads, shipping interests, Eastern and Gulf ports, private utility companies, and the coal-mining industry opposed the treaty, however, and the U.S. Senate refused to ratify it in 1934.

Tensions between the United States and Canada were often high as representatives of the two nations tried to work out an agreement that would satisfy both sides. It took 20 years for that agreement to be reached, but work on the hydroelectric project began in August 1954; construction started on the navigation phase one month later. The hydroelectric project generated its first power in the summer of 1958.

The seaway was opened to commercial traffic on April 25, 1959, and was dedicated by Queen Elizabeth II and President Dwight D. Eisenhower, at St. Lambert, on June 26, 1959. Over 2.5 billion tons of cargo have been shipped via the Seaway since its opening.

Queen Elizabeth II and President Dwight Eisenhower watch a fireworks display near Montreal from the royal yacht Britannia following dedication of the Seaway
dedication ceremony

a Mountie watches the first ship enter the St. Lawrence Seaway through the St. Lambert Lock, on April 25, 1959
St. Lawrence Seaway opens to traffic

Seaway Canals and Locks

South Shore Canal -- 14 nautical miles -- bypasses the Lachine Rapids at Montreal -- two Canadian locks, St. Lambert and Ste. Catherine.

St. Lambert Lock
St. Lambert Lock in 1959

St. Lambert Lock today
St. Lambert lock

Beauharnois Canal -- 11.3 nautical miles -- bypasses Beauharnois Power Plant at Beauharnois, Quebec -- two Canadian locks.

Wiley-Dondero Canal -- 8 nautical miles -- bypasses the Long Sault Dam and St. Lawrence Power Dam near Massena, New York -- two U.S. locks, Snell and Eisenhower.

aerial view of the Wiley-Dondero Canal and the dams it bypasses
Wiley-Dondero Canal

dedication of the Dwight D. Eisenhower Lock in July 1958
dedication of Eisenhower Lock

Snell Lock's gates open for the first time, 1958
Snell Lock

aerial view of Snell Lock soon after its completion
Snell Lock

Iroquis Canal -- 0.3 nautical miles -- bypasses the Iroquois Control Dam downriver from Massena, New York -- 1 Canadian lock.

Iroquis Lock, the first completed lock on the Seaway, was opened May 23, 1958
Iroquis Lock

Iroquois Control Dam and Canal as it looks today
Iroquois Control Dam and Canal

Welland Canal -- 23.5 nautical miles -- bypasses Niagara Falls, from St. Catharines to Port Claiborne, Ontario (Lake Ontario to Lake Erie) -- 8 Canadian locks.

locks on the Welland Canal
locks on the Welland Canal

St. Mary's Falls Canals -- Lake Huron to Lake Superior -- 4 parallel locks, including the Soo Locks at Sault Ste. Marie

Maximum Ship Dimensions

Length 740 feet
Beam 78 feet
Draft 26 feet 6 inches
Height Above Water 116 feet 6 inches

Great Lake St. Lawrence Seaway System

Jacques Cartier
Northwest Passage
Queen Elizabeth II
President Dwight D. Eisenhower
Soo Locks

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This page was last updated on June 25, 2018.