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St Lawrence Seaway

, North America




5 years


£272m (£5.8bn today)


North America
Project achievements

Economy boosted

$bn in business revenue has been possible thanks to the creation of the seaway.

Solved the problem

Create a channel to let ships sail from the Atlantic right into the great lakes. Previous

Used engineering skill

One of the biggest engineering challenges ever – to create locks and seaway.

Create a seaway to connect the Great Lakes of North America to the Atlantic Ocean

The St Lawrence Seaway is a system of locks, canals and channels linking the Great Lakes of Northern America with the Atlantic Ocean.

Acknowledged as one of the outstanding engineering achievements of the 20th century, the seaway opened in 1959. The 3,700km long route can take ships up to 225.5m long x 24m wide. The scheme is the longest navigation system in the world.

The scheme incorporates the earlier Welland canal between Lake Superior and Lake Erie, which was deepened as part of the project.

The seaway is not a continuous canal. The St Lawrence river section of the network consists of several stretches of navigable channels within the river. There are also locks and canals along the banks of the river to bypass rapids and dams.

There are 7 locks along the St Lawrence river section of the scheme and 8 locks on the Welland canal stretch. Each lock holds the equivalent of 30 Olympic size swimming pools of water.

The seaway plays a significant part in the economies of both Canada and the US – millions of tonnes of grain, steel and other commodities are shipped along the route every year.

The structure was formally opened in 1959 when the Queen and US President Dwight D. Eisenhower took a short cruise along part of the seaway on the royal yacht Britannia.

Did you know …

  1. The first proposals for the St Lawrence Seaway came from both Canadian and American politicians in the 1890s.

  2. As work didn't start for another 60 years, the scheme has been called 'the longest-running unresolved issue in Canada-US relations'.

  3. The seaway is the largest frontier project jointly undertaken by two countries.

Difference the seaway has made

Cargo shipments on the seaway generate an estimated $34.6bn of economic activity every year as well as jobs for 227,000 people in Canada and the US.

More than 160m tonnes of freight are moved along the route every year. Cargo includes coal for power stations, cement for construction and grain for domestic use and export.

The seaway is credited with providing a cost-effective, safe and environmentally-friendly method of moving raw materials, commodities and manufactured goods.

How the work was done

Construction of the seaway began in September 1954. Over 500 Canadian and American engineers directed more than 20,000 workers.

The scheme saw new locks built and canals dug – as well as the construction of bridges, new roads and railways.

Engineers faced early problems when mechanical excavators hit tough rock formations that slowed down progress digging canals. The project team had to design more powerful machinery for the scheme for work to continue.

A major part of the project was the construction of a dam near Cornwall, Ontario which created the reservoir Lake St Lawrence. The lake was designed as part of the seaway and was also intended to provide water for hydroelectric generation.

The project team had to relocate over 6,500 people so the dam could be built. Workers also moved 65km of railway track and 56km of roads.

The 6 villages and 3 hamlets submerged by the lake came to be known as the 'lost villages'.

It took 3 days and nights for the lost villages to disappear underwater when engineers flooded the dam in 1958.

People who made it happen

  • Clients: government of Canada, US government
  • Construction: US Army Corp of Engineers

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