Further work extended into the 19th century. The residential rooms were redecorated several times, and the Main Building and garden wing were built. This work was carried out by Nikolaus Friedrich von Thouret on the order of Duke Friedrich II, the first Württemberg king from 1806. In 1807 the palace was completely furnished. Rooms and halls were changed repeatedly up until the end of the monarchy.
Since 1918 the New Palace has been state-owned and at first served as a museum, which not only exhibited precious objects from the royal "Kunstkammer" (a collection of art, treasures and natural oddities from around the world) but also showed the Majolika collection and various period rooms (Stilzimmer).
In the last fifteen months of World War II the New Palace was reduce to a ruin in several bombing raids. A lively discussion was carried on from 1945 to 1954 on the further fate of the palace. The plans ranged from its complete demolition to the establishment of a health-resort hotel or the seat of the federal government to rebuilding and use as a museum. Finally, in 1957 the decision was made for its rebuilding and use for administrative purposes. Part of the rooms were restored in accordance with the original and are used by the state of Baden-Württemberg for representation purposes.