Ever since Prince Karl zu Nassau-Usingen had moved his residence to Biebrich Palace, Wiesbaden had played the role of a supra-regional political center. The continuation of this 200-year tradition was by no means a matter of course after the collapse of Nazi tyranny in 1945. Wiesbaden also suffered massive destruction as a result of the Second World War, but the effects were far less catastrophic than in Frankfurt, Kassel, Darmstadt, Hanau or other Hessian cities. On 28.03.1945, the troops of the US Army occupied Wiesbaden. The military government for the US occupation zone (OMGUS) took up residence in the IG Farben building in Frankfurt. From the municipal administrative level to the administrative districts to the former provinces, military government teams were deployed to reorganize public life in the city and the countryside. In Wiesbaden, too, the US military promoted a new democratic beginning with its strategy of "indirect rule" soon after the liberation from National Socialism. In order to create the most politically stable and economically viable administrative units possible, the Americans decided to establish Länder as the highest level of state organization in a federal Germany. After intensive deliberations on territorial reorganization on Hessian territory and with the involvement of the German side, the option of merging the Prussian administrative districts of Wiesbaden and Kassel with the People's State of Hesse to form a "Greater Hesse" gradually crystallized within the US military government in the summer.

Marburg, centrally located, was initially considered as the provisional capital of this new state. For various reasons, but above all because of the socio-economic weight of the Rhine-Main region, the US military opted for a "Greater Hesse" capital located there. The decision was finally made in favor of Wiesbaden, where the headquarters of the future state military administration had been established in the meantime. On September 19, 1945, OMGUS founded the state of "Greater Hesse" with its Proclamation No. 2. A few days later, OMGUS designated Wiesbaden as the seat of the state military government (OMGH) and as the state capital of "Greater Hesse". With his Organizational Order No. 1, the head of OMGH, Colonel Newman, formally implemented this fundamental decision on 12.10.1945: Wiesbaden was thus officially the capital of the state of "Greater Hesse", which was renamed "Hesse" with the adoption of the state constitution on 01.12.1946.