Physical features

The Saint Lawrence system is about 2,340 miles (3,770 kilometers) long. At its western end is the city of Duluth, Minnesota. Duluth is a port on Lake Superior, the westernmost of the five Great Lakes. Narrow waterways link the lakes to one another. The Saint Lawrence River itself begins at the eastern end of Lake Ontario, at the Canadian town of Kingston. It flows 740 miles (1,190 kilometers) to the Gulf of Saint Lawrence. Finally, the Cabot Strait connects the gulf to the Atlantic Ocean.

Along with natural waterways such as rivers and lakes, the Saint Lawrence Seaway includes waterways and structures made by people. These include canals, locks, and dams.

Canals are artificial waterways built to connect two natural bodies of water. The Welland Canal, for example, joins Lakes Ontario and Erie. At certain points along the Saint Lawrence River, canals are used to help ships avoid rapids. These are sections of the river where the water flow is rough and very fast.

Locks are enclosures that are either filled up or emptied to raise or lower a ship from one water level to another. They are needed because the water level varies between the different parts of the Saint Lawrence system. The water level of Lake Ontario, for example, is higher than that of the Saint Lawrence River. A ship leaving the lake must be lowered through locks before it can enter the river.

Dams are barriers built across rivers or streams to store water or control its flow. Along the seaway, dams are used to form lakes and create electricity by taking advantage of the flow of water.

Economy

The Saint Lawrence Seaway is a major trade route between the United States and Canada and between these two countries and the rest of the world. The most important goods shipped through the seaway are grain, iron ore, coal, iron, and steel. Major cities with ports on the seaway include Chicago, Milwaukee, Detroit, and Buffalo in the United States and Toronto, Montreal, and Quebec in Canada. Because ice forms in parts of the seaway in the winter, the shipping season is limited to about eight and a half months, from April to mid-December.

History

The French explorer Jacques Cartier explored the Gulf of Saint Lawrence in 1534. A year later he returned to the area and sailed up the Saint Lawrence River. In 1608 another Frenchman, Samuel de Champlain, founded the city of Quebec on the banks of the river. The Saint Lawrence became a well-traveled route for fur traders, explorers, and missionaries.

As early as 1700, French priests built a canal to help canoes travel around the Lachine Rapids on the river, near what is now Montreal. In 1829 a private company opened the first canal to allow ships to go around Niagara Falls. The first set of locks on what would become the seaway were opened in 1855 at Sault Sainte Marie, Michigan. (See also Sault Sainte Marie canals.)

From the start of the 20th century, Canada and the United States discussed building a seaway that would open the Great Lakes to the ocean. For a long time, though, the United States was not as willing to commit to the project as Canada was. In 1932 the U.S. Congress refused to approve a treaty worked out by the two countries. In 1954, however, Congress passed a law that created the Saint Lawrence Seaway Development Corporation. The corporation was to work with the Saint Lawrence Seaway Authority of Canada in the construction of the new seaway.

The seaway project was a great feat of engineering. Construction began in the summer of 1954 and took almost five years to complete. About 22,000 people worked on the project. They built canals, locks, and dams along the Saint Lawrence River. They also deepened a number of other waterways. These included the Straits of Mackinac, between Lakes Michigan and Huron; the Saint Marys River, between Lakes Superior and Huron; and the Detroit River, Lake Saint Clair, and the Saint Clair River, between Lakes Erie and Huron. Dams along the seaway began producing electric power in 1958. The seaway was opened to ships in 1959.