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Major Lakes, Great Lakes
lake traffic, meltwater, containerships, ice sheet, Lawrence Seaway
The Great Lakes, forming the largest continuous freshwater body in the world, include five massive inland lakes (Superior, Huron, Michigan, Ontario, and Erie), encompassing 244,100 sq km (94,250 sq mi) in the upper reaches of the midwestern United States. Lake Michigan is the only one of the lakes that is located entirely in the United States. The other four lakes lie on the border between the United States and Canada.
Several thousand years ago, these enormous water features were shaped when an ice sheet extended over the region and created five large depressions. As the ice sheet receded, meltwater filled the basins and created the lakes. While many streams and rivers flow into the Great Lakes, the St. Lawrence, beset with rapids and waterfalls, offers the only natural outlet to the Atlantic Ocean.
During the early part of the 19th century, the Great Lakes were of only limited value as a transportation route because rapids and waterfalls prevented ships from traveling across the Great Lakes and down the St. Lawrence to the Atlantic Ocean.
Transportation improved when a number of canals were built between the various lakes and between the lakes and the Atlantic Ocean. The Erie Canal, connecting Lake Erie with New York’s Hudson River, opened in 1825. The canal offered the first navigable water connection to the East Coast from the lakes region. Small ships and barges began to move raw materials and supplies to and from the Great Lakes area. The Welland Ship Canal, built in 1829 to bypass Niagara Falls, made the Great Lakes accessible to small oceangoing vessels via the St. Lawrence River. In 1855 the Sault Sainte Marie Canal opened, enabling lake traffic to proceed from Lake Superior to Lake Huron. As settlers began to flow into the Great Lakes territory, inland port cities and other urban settlements grew.
In the late 1950s, the U.S. and Canadian governments cooperated to build the St. Lawrence Seaway to allow large oceangoing vessels access to the Great Lakes. The seaway consists of 720 km (450 mi) of improvements to the St. Lawrence River, which flows mainly through Canada. These improvements included numerous locks and canals between Lake Erie and Montreal, Canada. The Seaway’s 8.2-meter-deep (27-foot-deep) channel is not adequate to handle today’s largest oceangoing vessels and containerships.
The Great Lakes-St. Lawrence system is a waterway of major commercial importance, even though it is open for navigation only nine months of the year. In the winter, ice blocks the channels and the edges of the lakes. This waterway is used to ship bulk cargo, including iron ore, grain, limestone, timber, and coal, among inland ports of the region, the Atlantic coast, and beyond. It has allowed many Great Lakes port cities to become international trade centers.
Today, almost 20 percent of the U.S. population lives along the shores of the Great Lakes, concentrated in five large cities: Chicago, Illinois; Milwaukee, Wisconsin; Detroit, Michigan; Cleveland, Ohio; and Buffalo, New York. These urban centers benefit greatly because of the movement and manufacture of goods throughout the Great Lakes region.
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