Württemberg-Hohenzollern should not be confused with the larger Gau ("shire") of the same name that was formed briefly during the Third Reich.
Württemberg-Hohenzollern consisted of the southern half of the former state of Württemberg and the Prussian administrative region of Hohenzollern. The northern half of Württemberg became the state of Württemberg-Baden under US-administration. The division between north and south was set so that the Autobahn connecting Karlsruhe and Munich (today the A8) was completely contained within the American zone.
On 18 May 1947, a new constitution was enacted and Württemberg-Baden's first parliament was elected. With the formation of West Germany on 23 May 1949, Württemberg-Baden joined the federal republic.