Friedberg Castle, perched on a rise overlooking the Inn valley, was built in the thirteenth century. In 1844 it was acquired by Count Trapp, who renovated it from 1847 to 1854. The castle is owned today by the family. Oswald Trapp, who moved to Friedberg in 1930, was curator of the weapons collection at the Tiroler Landesmuseum Ferdinandeum and from 1937 to 1946 was chairman of the museum association. He was also Landeskonservator (head curator) of Tyrol from 1934 to 1960. In July 1943 he made the castle available as a depot for artworks from the Ferdinandeum. The most valuable examples of minor art and the prehistoric and patriotic collection were stored in the castle archive and the most important sculptures and some of the library (e.g., the Fischnaler library catalogue) were deposited in the castle chapel. Privately owned objects were also stored there. The decision adopted in autumn 1943 to store the Ferdinandeum's zoological collection in the castle was not implemented because of transport difficulties. Instead, the newspapers from the Ferdinandeum library, the museum files and the salvage lists were stored in Friedberg. The museum employee Gretl Köllensperger, who moved to Friedberg Castle in autumn 1944, continued the work on the library files there. By the end of 1945, the objects had been returned to the museum.

By order of Franz Hofer, Gauleiter of Tyrol-Vorarlberg, as Oberster Kommissar für die Operationszone Alpenvorland (Supreme Commissar for the Operational Zone of the Alpine Foothills), three crates were brought to Friedberg Castle in January 1945 for storage. In 1951 these crates were opened in the Tiroler Landesmuseum and the contents, including works by Albin Egger-Lienz, were inventoried by the museum. Previous owners of these works still remain unidentified today.