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FreightWaves Classics: St. Lawrence Seaway connects mid-North America to the world

The H2O Highway is a key transportation route for North America

A ship moving through the St. Lawrence Seaway. (Photo: Great Lakes St. Lawrence Seaway System)

The 63rd navigation season on the Great Lakes-St. Lawrence Seaway System was launched on March 22nd during an official opening ceremony.

“Moving goods by water through the Seaway ensures trade is flowing freely between the U.S.
and Canada while also reducing emissions,” said U.S. Secretary of Transportation Pete Buttigieg.
“After 62 years of operation, the binational Seaway System remains a model of international
cooperation and partnership and showcases how we can work together to address the challenges
of climate change.”


Before either the United States or Canada became countries, the Great Lakes and the St. Lawrence River served as major North American trade arteries. But there was no way to reach the Great Lakes from the Atlantic Ocean prior to the construction of the St. Lawrence Seaway.

The St. Lawrence Seaway is a system of locks, canals and channels in the two countries that permits certain oceangoing vessels to travel from the Atlantic Ocean to the Great Lakes, as far inland as Duluth, Minnesota, which is located at the western end of Lake Superior. Together, the St. Lawrence River and the Great Lakes are the longest deep-draft navigation system in the world, extending into the North American heartland. The system includes the five Great Lakes and their connecting channels, as well as the St. Lawrence River to the Gulf of St. Lawrence.

Called the “H2O Highway” or “Highway H2O” by many, it is a 2,300-mile waterway that runs between Canada and the United States. It comprises the St. Lawrence River, St. Lawrence Seaway and the Great Lakes. The St. Lawrence Seaway was built as a binational partnership between the U.S. and Canada, and continues to operate as such.

The St. Lawrence River portion of the seaway is not a continuous canal; it consists of several stretches of navigable channels within the river, as well as a number of locks and canals that parallel the river’s banks in order to avoid rapids and dams. 

Over the last 200 years, improvements in Canada and the U.S. have enhanced the waterway. In 1829, the Welland Canal was built to connect Lake Ontario and Lake Erie, enabling vessels to bypass Niagara Falls. The Soo Locks made the St. Marys River navigable, connecting Lake Superior to the lower four Great Lakes and the St. Lawrence Seaway. 

Construction of the 189-mile St. Lawrence Seaway began a new era in marine transportation for the two nations. Begun in 1954 and finished in 1959, the Seaway was one of the most challenging engineering feats in history. Seven locks were built (five in Canada and two in the U.S.). Together, they lift ships 246 feet above sea level as they move from Montreal to Lake Ontario.

A ship docked along the St. Lawrence Seaway. (Photo: Great Lakes St. Lawrence Seaway System)
A ship docked along the St. Lawrence Seaway. (Photo: Great Lakes-St. Lawrence Seaway System)

During the construction of the Seaway, about 22,000 workers collectively moved 210 million cubic yards of earth and rock and poured over 6 million cubic yards of concrete. The Seaway is considered to be one of the 20th century’s key engineering feats.

The Seaway supports activities at more than 100 ports and commercial docks located in the eight Great Lakes states and the provinces of Ontario and Quebec. It is a crucial transportation network for goods moving between North America and 60 overseas markets.

The logo of the Seaway System. (Image: Great Lakes-St. Lawrence Seaway System)
The logo of the Seaway System. (Image: Great Lakes-St. Lawrence Seaway System)

Facts and figures

This deep-draft inland navigation system is the longest in the world, extending from the Atlantic Ocean into the North American heartland. As a bi-national trade corridor, the Seaway complements the region’s rail and highway networks and provides a cost-effective, reliable and environmentally smart method of moving raw materials, agricultural commodities and manufactured products to and from domestic and global markets. More than 160 million metric tons of raw materials, agricultural commodities and manufactured products are moved on the Great Lakes-St. Lawrence Seaway System annually. Key cargoes include iron ore for steel production, coal for power generation, limestone and cement for construction, and grain for both domestic consumption and export. Other major cargoes include aluminum, machinery, sugar, fertilizers, road salt, petroleum products and containerized goods. 

The Seaway is used by three distinct groups. American and Canadian domestic carriers transport cargo between ports within the Seaway system, and international ocean-going vessels operate between ports within the system and ports located overseas. Pleasure craft also use the system. 

This photo shows all the types of ships and boats that use the Seaway. (Photo: Great Lakes St. Lawrence Seaway System)
This photo shows all the types of ships and boats that use the Seaway. (Photo: Great Lakes-St. Lawrence Seaway System)

None of this would be possible without the series of locks. Seven locks are located on the Montreal-Lake Ontario section of the St. Lawrence Seaway. Together these locks lift/lower ships 226 feet. Eight locks located along the Welland Canal section of the Seaway lift/lower ships 326 feet; and one lock at Sault Ste. Marie, Michigan, lifts/lowers ships 30 feet. A ship transiting the Seaway’s 15 locks from Montreal to Lake Erie crosses the international border 27 times.

Economic impact

To commemorate the 63rd season of the Seaway, U.S. Great Lakes-St. Lawrence Seaway Development Corporation Deputy Administrator Craig H. Middlebrook said, “Commercial navigation on the Great Lakes-St. Lawrence Seaway System is an economic foundation of the U.S. and Canadian economies.  More than 237,000 jobs and $35 billion in economic activity in the U.S. and Canada are annually supported by movement of various cargoes on the Great Lakes-St. Lawrence Seaway System.”

Highway H2O flows directly into the commercial, industrial and agricultural heartlands of the two nations. The area has a population of 100 million people, which is about one-quarter of the combined Canada/U.S. population.

The Great Lakes and the St. Lawrence River were a means of transportation for Native Americans and the earliest European explorers, trappers and settlers. Many towns and cities on the banks of the Great Lakes were founded as trading posts that enabled commerce in the era predating railroads and roads. The Great Lakes-St. Lawrence region is the industrial and agricultural heartland of both the United States and Canada – with a combined GDP of more than $6 trillion. This output would represent the world’s third-largest economy – behind the U.S. and China – if it were a country.

Unloading a different, but important cargo along the Seaway. (Photo: Great Lakes St. Lawrence Seaway System)
Unloading a different, but important cargo along the Seaway. (Photo: Great Lakes-St. Lawrence Seaway System)

In addition to locks, ships and ports, thousands of maritime service providers work to ensure the safe, reliable and efficient transport of cargo. Service providers include stevedores, warehouse employees, freight forwarders, dockworkers, crane operators, vessel agents, dredging contractors, marine pilots, truck drivers and port rail operators, tugboat operators and shipyard workers.

From 2009-18 over $5.64 billion was spent to improve the St. Lawrence Seaway System. This included capital spending on ships, ports, terminals and waterway infrastructure.

The Canadian and U.S. federal governments dedicated nearly $1 billion to modernize the Seaway’s lock infrastructure and technology over that same 10-year period. This was the Seaway’s most significant transformation in more than 50 years. Great Lakes and St. Lawrence River ports and terminals also collectively invested more than $1.8 billion to expand their docks, equipment, facilities and intermodal connections.

Pleasure craft and ships on the Seaway. (Photo: Great Lakes St. Lawrence Seaway System)
Pleasure craft and ships on the Seaway. (Photo: Great Lakes-St. Lawrence Seaway System)


Several other canals preceded the Saint Lawrence Seaway. Locks built on the Saint Lawrence River in 1871 allowed transit of large vessels (up to 186 feet long, 44 feet wide, and 9 feet deep). The first Welland Canal, constructed between 1824 and 1829, had a minimum lock size of 110 feet long, 22 feet wide and 8 feet deep. However, it was too small to allow passage of larger oceangoing ships. The second Welland Canal was larger, wider and deeper; the third Welland Canal was even bigger. The fourth (and current) Welland Canal’s locks are 766 feet long, 80 feet wide and 30 feet deep. 

In the 1890s the first proposals surfaced for a binational, comprehensive deep waterway along the Saint Lawrence River. In the decades that followed, developers proposed hydropower projects tied to the seaway. Supporters believed the deeper waterway created by the hydro project would make the seaway channels feasible for oceangoing ships. However, U.S. proposals for development through the end of World War I were not favored by the various Canadian federal governments. Nonetheless, the two national governments submitted plans for study. By the early 1920s, both the Wooten-Bowden Report and the International Joint Commission recommended the project.

Although not a supporter of the project, Prime Minister Mackenzie King and the U.S. representative signed a treaty of intent in 1932. Submitted to the U.S. Senate in November 1932, hearings were held on the proposal during 1933; a vote was taken on March 14, 1934. While a majority of the Senate voted in favor of the treaty, it fell short of the necessary two-thirds vote for ratification. Other attempts between the governments in the 1930s also failed due to opposition by the Ontario and Quebec provincial governments. 

Along the Canadian shore of the seaway. (Photo: Great Lakes St. Lawrence Seaway System)
Along the Canadian shore of the seaway. (Photo: Great Lakes-St. Lawrence Seaway System)

In 1936, a delegation of eight representatives from the Great Lakes met at the White House with President Franklin D. Roosevelt to obtain his support for the seaway concept.

Seaway proponents argued that a nautical link would lead to development of the communities and economies of the Great Lakes region by permitting the passage of oceangoing ships. In the depths of the Great Depression, exports of grain and other commodities to Europe were an important part of the national economy. Negotiations on the treaty began again in 1938; by January 1940 substantial agreement was reached between the two nations. By 1941, President Roosevelt and Prime Minister King signed an executive agreement to build the joint hydro and navigation works, but this failed to receive the approval of Congress. Proposals for the seaway were met with resistance based on economic reasons. The primary opposition came from interests representing Atlantic and Gulf coast harbors, internal waterways and the railroads. 

After World War II ended, proposals to introduce tolls to the seaway were also defeated in Congress. However, the province of Ontario needed the energy that would be generated by hydroelectricity, and Canada began to consider developing the project by itself. The plan became popular and appealed to Canadian nationalism. On September 28, 1951, Canadian Prime Minister Louis St. Laurent told President Harry Truman that Canada was unwilling to wait any longer for U.S. participation and would build a seaway by itself. The Canadian Parliament approved the Saint Lawrence Seaway Authority on December 21, 1951. Canada would construct the waterway, as well as the Moses-Saunders Power Dam. The dam became a joint responsibility of Ontario and New York because a hydropower dam would impact water levels in New York as well as Canada.

A ship passes through one of the bridges along the Seaway. 
(Photo: Great Lakes St. Lawrence Seaway System)
A ship passes through one of the bridges along the Seaway.
(Photo: Great Lakes-St. Lawrence Seaway System)

The International Joint Commission issued an order of approval for joint construction of the dam in October 1952. While it took quite a while, the order of approval was agreed to by the Senate and House in May 1954. The first positive action to enlarge the seaway was taken on May 13, 1954. President Dwight D. Eisenhower signed the Wiley-Dondero Seaway Act, which authorized joint construction and established the Saint Lawrence Seaway Development Corporation as the U.S. authority. On August 10, 1954, groundbreaking ceremonies took place in Massena, New York. 

The Connecting Channels Project was begun by the U.S. Army Corps of Engineers in May 1957. By 1959, the U.S. Coast Guard cutter Maple made the first trip through the U.S. locks, which opened up the Great Lakes to ocean-going ships. On April 25, 1959, large, deep-draft ocean vessels began moving along the seaway to the heart of North America. 

The seaway cost C$470 million. Of that amount, $336.2 million was paid by the Canadian government. Queen Elizabeth and President Eisenhower formally opened the seaway with a short cruise aboard the royal yacht HMY Britannia after addressing crowds in Saint-Lambert, Quebec. 

Administration of the system is handled by the Saint Lawrence Seaway Development Corp. in the U.S., a federal agency within the U.S. Department of Transportation. The St. Lawrence Seaway Management Corporation is a not-for-profit corporation that oversees Canada’s involvement; ownership of the Canadian portion of the Seaway remains with the Canadian federal government.

Great Lakes and seaway shipping generates more than $3.5 billion in business revenue annually in the United States. However, international changes have impacted seaway shipping.  Europe is no longer a major grain importer; large-scale U.S. grain shipments now go to South America, Asia and Africa. That means much of the grain is shipped from Gulf of Mexico and West Coast ports rather than through the Seaway. 

Referring to the seaway project, a retired Iowa State University economics professor who specialized in transportation issues said, “It probably did make sense, at about the time it [the Seaway] was constructed and conceived, but since then everything has changed.”

An aerial view of one of the locks along the Seaway. (Photo: Great Lakes St. Lawrence Seaway System)
An aerial view of one of the locks along the Seaway. (Photo: Great Lakes-St. Lawrence Seaway System)

Expansion proposal

The size of vessels that can use the seaway is limited by the size of its locks. Although the Panama Canal is much older than the seaway, its original 1914 locks were larger than the seaway’s locks. When the seaway was being designed in the 1950s, the decision was made not to build the seaway’s locks to match the size of ships permitted by the Panama Canal’s 1914 locks. Ships of this size are known as Panamax ships, meaning they can transit the Panama Canal without difficulty. The decision was made that the seaway’s locks would be the same size as the smaller locks of the Welland Canal. The largest vessels that can use the seaway locks are known as Seawaymax ships, and they are small ships by today’s standards. (The Panama Canal was greatly improved in the last few years and can handle even bigger ships than the Panamax-class ships that were built specifically to transit the canal.)

The draft of vessels is another obstacle to passage on the seaway, particularly in connecting waterways such as the Saint Lawrence River. The depth in the seaway’s channels is between 27 and 41 feet deep. Channel depths and limited lock sizes mean that only 10% of current oceangoing ships can travel along the entire length of the seaway. Expansion proposals (some dating from as early as the 1960s), have been rejected as too costly. In addition, researchers, policymakers and the public are more aware of the environmental issues that impacted development of the seaway and do not want more invasive and damaging species in the Great Lakes, the canals or the river. Lower water levels in the Great Lakes have also posed problems for some vessels in recent years, and pose greater issues to communities, industries and agriculture in the region.

The MV Damia Desgagnes unloads liquified natural gas at Pier 22 in Hamilton, Ontario. 
(Photo: Chamber of Marine Commerce)
The MV Damia Desgagnes unloads liquified natural gas at Pier 22 in Hamilton, Ontario.
(Photo: Chamber of Marine Commerce)


The seaway is still very important for American and Canadian international trade. It handles 40 to 50 million tons of cargo each year. Approximately 50% of this cargo travels to and from ports in Europe, the Middle East and Africa. The remaining 50% is coastal trade or short sea shipping between American and Canadian ports. And, since 1997, international cruise liners have used the seaway as an excursion for passengers. 

However, the seaway’s physical limitations will continue to impact its economic importance. If only 10% of the seagoing ships in the world can use the seaway now, that number will continue to decline as new and bigger ships come online.

Note: Information and photos for this article came predominantly from the Great Lakes-St. Lawrence Seaway website. If you would care to learn more, here is a link to that website.

One Comment

  1. NIckSJ

    If Biden’s “infrastructure” package was actually about infrastructure, rebuilding the Seaway to accommodate large containerships and bulk carriers would revolutionize transportation of imports and exports throughout the center of both countries. However, the environmental movement has virtually ended the ability of either country to make rational infrastructure investments. China has now overtaken the West on infrastructure developments, while the US and Canada sit dead in the water thanks to environmentalist obstructionism.

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Scott Mall

Scott Mall serves as Managing Editor of FreightWaves Classics. He writes articles for the website, edits the SONAR Daily Watch series, marketing material for FreightWaves and a variety of FreightWaves special projects. Mall’s career spans 45 years in public relations, marketing and communications for Fortune 500 corporations, international non-profits, public relations agencies and government agencies.