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Which Great Lake lies entirely within the United States?

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Great Lakes Marquette Harbor Lighthouse on Lake Superior, Marquette, Michigan.

Lake Michigan is the only one of the five Great Lakes that lies entirely within the United States. While the other four lakes—Superior, Huron, Erie, and Ontario—form a natural border between the United States and Canada, Lake Michigan is bordered exclusively by the U.S. states of Michigan, Wisconsin, Illinois, and Indiana.12