The Great Lakes form the world's largest body of fresh water and, with their connecting waterways, are also the largest inland water transportation unit in the world. Draining the great North Central basin of the United States, they enable shipping to reach the Atlantic via their outlet, the St. Lawrence River, and to reach the Gulf of Mexico via the Illinois Waterway. A third outlet connects with the Hudson River and then the Atlantic via the New York State Barge Canal System.

Ships move from the shores of Lake Superior to Whitefish Bay at the east end of the lake, then through the Soo (Sault Ste. Marie) Locks, through the St. Mary's River and into Lake Huron. To reach Gary and the Port of Indiana and South Chicago, Illinois, ships move west from Lake Huron to Lake Michigan through the Straits of Mackinac. To continue on towards the St. Lawrence River, ships move south out of Lake Huron down the St. Clair River, through Lake St. Clair, and on in to Lake Erie. They must then navigate the Welland Canal, which bypasses Niagara Falls, pass through Lake Ontario, and then navigate the St. Lawrence Seaway. Total sailing distance from Duluth, Minnesota, to the eastern end of Lake Ontario is 1,156 miles.

The Great Lakes were formed about 250,000 years ago when a glacier moved south across the land of what is now the Great Lakes region. The glacier dug out deep depressions in the soft rocks of the region and picked up great amounts of earth and rocks. The glacier withdrew between 11,000 and 15,000 years ago, and the earth and rocks blocked the natural drainage of the depressions. Water from the melting glacier gradually filled in the depressions and formed the Great Lakes.

About the Lakes

The Great Lakes in Profile

See Also

Soo (Sault Ste. Marie) Locks
Niagara Falls
St. Lawrence Seaway

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This page was last updated on December 21, 2018.