A group of five connected freshwater lakes, the Great Lakes include (from largest to smallest) Lake Superior, Lake Huron, Lake Michigan, Lake Erie, and Lake Ontario. The St. Lawrence Seaway, a set of canals and locks, links the Great Lakes with the St. Lawrence River and the Atlantic Ocean. Linked with the sea, the lakes provide an important commercial waterway for the industrial and agricultural economies of the area. This map illustrates the Great Lakes and shows their location in the north central portion of the United States and south central portion of Canada.