Hartheim Castle was built in the early 17th century and is one of the most important Renaissance buildings in Austria. In the late 19th century its then owner, Prince Starhemberg, donated it to the Upper Austrian State Charitable Association for the purpose of caring for mentally and physically disabled people. In 1898, this organisation established a so-called “institution for the feebleminded, imbecile, idiotic and cretinous” in the castle. In the period before 1940, people with disabilities were cared for here by the Merciful Sisters of St. Vincent de Paul. After the “Anschluss” (“Annexation”) of Austria to the German Reich, the Upper Austrian State Charitable Association was disbanded in December 1938, and the management of the institution was handed over to the care department of the “autonomous administration” of the Gau, or Nazi administrative district. The association’s property, including the castle, then became part of the Upper Danube Gau.