The Great Lakes Union of Communes or Great Lakes Union is one of America's ten constituent republics. It is bordered by the People's Republic of New England to the east, the People's Republic of Appalachia to the southeast, the Democratic People's Republics of the Heartland to the southwest, and the Rocky Mountain Socialist Union to the west.

The Great Lakes Union is the origin of the UAPR and the stronghold of the American Communist Party. The Union's capital, Detroit, was the first city to declare itself a commune during the Second American Civil War, and served as the UAPR's capital city until the end of the war. The Great Lakes Union of Communes is the industrial heartland of America, containing major cities such as Detroit, Chicago, Cleveland, Cincinnati, Indianapolis, and Milwaukee.

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