Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is bordered by the states of Wisconsin, Illinois, Indiana, and Michigan, after which it is named. Through the Straits of Mackinac it is connected to Lake Huron, and together they are often treated as a single hydrological body.
With a surface area of about 22,400 square miles (58,000 km²), Lake Michigan is the second-largest of the Great Lakes by volume and the third-largest by surface area. Its shoreline stretches from the wooded dunes and beaches of Michigan and Wisconsin to the urban waterfronts of Chicago and other lakeside cities. Major inlets and bays include Green Bay and Grand Traverse Bay.
The lake is an important source of freshwater, transportation, recreation, and economic activity. Commercial shipping, fishing, tourism, and shoreline development all depend on it, while its beaches, parks, and dune systems make it a major natural landmark in the region. Lake Michigan also plays a significant role in the climate of surrounding areas, moderating temperatures and influencing local weather patterns.