The Great Lakes – St. Lawrence Seaway

The Great Lakes of North America — Superior, Michigan, Huron, Erie, and Ontario — together form the largest group of freshwater lakes on Earth. But their real significance in transport comes from the fact that they are linked to each other and to the Atlantic Ocean by a system of canals and the St. Lawrence River. This entire network is called the Great Lakes – St. Lawrence Seaway.

The key connections are the Soo Canal (between Lake Superior and Lake Huron) and the Welland Canal (which bypasses Niagara Falls between Lake Erie and Lake Ontario). These canals turn the separate lakes into one continuous inland waterway. From Lake Ontario, the St. Lawrence River flows northeast into the Atlantic, completing the route.

What makes this seaway unique is that it pushes ocean navigation deep into the continent. Ports like Duluth (on Lake Superior) and Buffalo (on Lake Erie) are equipped with all the facilities of ocean ports, even though they are hundreds of kilometres from the sea. Large ocean-going vessels can sail up the St. Lawrence River as far as Montreal.

However, beyond Montreal, the river has rapids that block large ships. Here, goods must be trans-shipped — moved from large ocean vessels to smaller ships that can continue through the shallower canals. To manage this, canals have been built to a depth of 3.5 metres, allowing smaller vessels to navigate around the rapids.