List of bridges over the St. Lawrence

The St. Lawrence River Basin.

This is a list of bridges over the St. Lawrence in Canada and the United States. The St. Lawrence River (French: Saint-Laurent) is a 500-kilometer-long river that connects the Great Lakes to the Atlantic Ocean. The mouth of the St. Lawrence forms a huge estuary in eastern Canada. The St. Lawrence played an important role in the early history of Canada, the oldest cities are located on it.

The St. Lawrence begins at the outlet of Lake Ontario, but the drainage basin encompasses the entire Great Lakes region in the United States and Canada. The transition from Lake Ontario to the St. Lawrence is at Kingston, Ontario. The river here is wide with large river islands and forms the border with the United States, initially New York State. The border with New York is between 1 and 2 kilometers wide, from Brockville it forms more clearly a river and no longer a lake with islands. The last major riverside town in Ontario is Cornwall. The only significant New York town on the St. Lawrence is Ogdenville.

The river then flows into the province of Québec. The large metropolitan area of Montréal soon lies on the river, which is called here in French the Saint-Laurent. The river has a very large torrent valley that is one of the most cultivated parts of Eastern Canada. Just before Montreal, the Ottawa River flows into the St. Lawrence, Montreal is on an island here. The river flows in a northeasterly direction and sometimes has more of a lake character. Important cities on the most downstream part of the river are Sorel-Tracy, Trois-Rivières and finally the city of Québec.

After the city of Québec, the river turns into an ever-widening estuary. Initially, the Île d’Orléans lies in the estuary, the estuary is then 15 kilometers wide and gradually becomes wider to more than 100 kilometers. At the transition from the estuary to the Gulf of St. Lawrence is the large le d’Anticosti. The estuary here turns into the open sea.


The Pont de Québec, the most iconic bridge over the St. Lawrence.

River Length
Oswegatchie River 220 km
Ottawa River (Ouatouais) 1,271 km
Richelieu River 124 km
Saint Francois River 218 km
Saint-Maurice River 563 km
Chaudiere River 185 km
Saguenay River 170 km
Manicouagan River 200 km


There are 7 weirs with locks in the St. Lawrence River to bridge the difference in height between the sea and Lake Ontario (74 meters). The first dam upstream is Beauharnois, a hydroelectric power station. There is also a hydroelectric power station at Cornwall and a weir at Iroquois, Ontario. None of these dams function as a public road connection, although there is a bridge just in front of the Beauharnois dam.


The Pont Laviolette at Trois-Rivières.

The average flow rate in the city of Québec is 12,100 m³/s, making the St. Lawrence about six times the size of the Rhine, but about a third smaller than the Mississippi River. Nearly half of the water in Québec flows into the St. Lawrence.

Due to the wide valley and the Great Lakes, floods do not usually occur. However, ice formation is a problem, especially in Québec.

The St. Lawrence as a waterway

The St. Lawrence has been transformed into a major waterway, the St. Lawrence Seaway. This is a system of canals and locks that allow ocean-going vessels to reach the Great Lakes all the way to Duluth, Minnesota. Another important part of this is the Welland Canal between Lake Erie and Lake Ontario.

The St. Lawrence Seaway is not a continuous channel between Lake Ontario and the open sea, but a mix of free-flowing river and lateral channels on shallow parts. There are seven locks for shipping between Montreal and Iroquois, Ontario. Further south, there are eight locks on the Welland Canal that bridge the height difference between Lake Erie and Lake Ontario. This also bypasses Niagara Falls.

It has been possible for ships to reach the Great Lakes since 1829, leading to industrialization in the region, particularly around Detroit and Cleveland. It also allowed ore to be transported from Minnesota across the Great Lakes to sea, although most ore remains internal to the Great Lakes region.

The St. Lawrence Seaway opened in 1959 as a modernized, larger-scale waterway that allowed large ocean-going vessels to reach the Great Lakes. After the opening of the St. Lawrence Seaway, the Erie Canal between Lake Erie and the Hudson River fell into disrepair, and with it much of the industry in Upstate New York, as the St. Lawrence Seaway had a much greater capacity than the Erie canal.

However, use of the St. Lawrence Seaway declined as Europe began to import less and less grain from the United States and Canada. These grain exports went more to South America, Asia and Africa, with these shipments more often going through the Mississippi River and no longer through the St. Lawrence.

For ships on the St. Lawrence, there is a size limit called the Seawaymax. These are the largest ships that pass through the locks of the St. Lawrence Seaway, they are ships of 230 meters in length, 24 meters in beam and 8.1 meters in draft. Cargo ships larger than these dimensions sail on the Great Lakes and thus cannot reach the ocean. However, there is no need to increase the capacity of the St. Lawrence Seaway.


In 1860, the first bridge over the St. Lawrence was opened, the Pont Victoria in Montreal. This was originally a railway bridge. In 1919, the Pont de Québec in Québec opened to traffic, which is still the largest cantilever bridge in the world. A number of bridges were opened in the 1930s, including the Thousand Islands Bridge. Most of the other bridges date from the 1960s. No new bridges were built across the St. Lawrence between 1969 and 2012.

List of bridges over the St. Lawrence

The Ogdensburg-Prescott International Bridge.

The list runs upstream from the mouth to Lake Ontario.

Bridge Route Length main span Type lanes Opening
Pont de Quebec 987 m 549 m cantilever bridge 1×3 1919
Pont Pierre-Laporte 1041 m 667 m suspension bridge 2×3 1969
Pont Laviolette 2707 m 335 m arch bridge 2×2 1967
Pont-Tunnel Louis-Hippolyte-La Fontaine 1391 m immersion tunnel 2×3 1967
Pont Jacques Cartier 2725 m 591 m cantilever bridge 1×5 1930
Pont Victoria 1800 m ? m truss bridge 2×1 1860
Pont Champlain 3440 m 215 m cantilever truss bridge 2×3 1962
Pont Honoré-Mercier 1361 m ? arch bridge 2×2 1934
Pont Serge-Marcil 1860 m ? box girder bridge 2×2 2012
Seaway International Bridge 1652 m ? truss bridge 1×2 1962
Ogdensburg-Prescott International Bridge 2250 m 351 m suspension bridge 1×2 1960
Thousand Islands Bridge 13700 m 240 m suspension bridge 1×2 1937


The St. Lawrence River Basin