The Great Lakes, sometimes disambiguated as the Laurentian Great Lakes, are a collection of freshwater lakes located in northeastern North America, on the Canada–United States border, which connect to the Atlantic Ocean through the Saint Lawrence Seaway and the Great Lakes Waterway. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth, containing 21% of the world's surface fresh water. The total surface is 94,250 square miles (244,106 km2), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km3). The lakes are sometimes referred to as the North Coast or "Third Coast" by some citizens of the United States.
The Great Lakes began to form at the end of the last glacial period around 10,000 years ago, as retreating ice sheets carved basins into the land and they became filled with meltwater. The lakes have been a major source of trade through their region, and are home to a large number of aquatic species. Many invasive species have been introduced due to trade in the area, and some threaten the region's biodiversity.
Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. The other four Great Lakes are shared by the U.S. and Canada. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron (and is slightly smaller than the U.S. state of West Virginia). To the east, its basin is conjoined with that of Lake Huron through the wide Straits of Mackinac, giving it the same surface elevation as its easterly counterpart; the two are technically a single lake. Lake Michigan is bounded, from west to east, by the U.S. states of Wisconsin, Illinois, Indiana, and Michigan. The word "Michigan" originally referred to the lake itself, and is believed to come from the Ojibwa word mishigami meaning "great water".