Lake Michigan
The only Great Lake entirely within the United States
Lake Michigan is the second-largest Great Lake by volume and the only one of the five that lies entirely within the United States. Spanning about 22,400 square miles (58,000 km²), it stretches some 300 miles north to south, bordered by Wisconsin, Illinois, Indiana, and Michigan. Chicago, Milwaukee, and a string of other cities line its shores, and Lake Michigan and Lake Huron are technically one body of water, joined at the Straits of Mackinac.
Glaciers gouged the lake's basin and left behind the world's largest freshwater dunes along its eastern shore, where prevailing winds pile sand into towering hills. The lake moderates the climate of the surrounding region and feeds a "lake effect" that buries the downwind shores in heavy winter snow. Its sandy beaches and clear water make it a summer playground for the millions who live around it.