After World War II, the northernmost areas of Upper Swabia became part of the American occupation zone, while the larger, southern area became part of the French occupation zone. In 1946, the Allied authorities founded the states of Württemberg-Baden and Württemberg-Hohenzollern, the borders of which ran along the borders of the occupation zones. As a consequence, the northern areas of Upper Swabia became part of the state of Württemberg-Baden and the southern areas became part of the state of Württemberg-Hohenzollern. Both states joined the Federal Republic of Germany on its founding in 1949. This situation lasted until 1952, when, following a referendum the previous year, Württemberg-Baden and Württemberg-Hohenzollern together with Baden created the new federal state of Baden-Württemberg.