in 1583, the landgrave of hesse-kassel became the sole owner of the lordship of schmalkalden, which had been shared with the counts of henneberg until then. landgrave william iv immediately decided to make the city one of his secondary residences. he had the 12th century waltaff castle demolished and began the construction of the castle named after him on the same location. the castle was inaugurated on 23 may 1590, although it had not yet been completed. the interior was procured from kassel. william's son maurice often stayed at wilhelmsburg castle. during his reign, the castle was finally completed in 1618. his successors used the castle less and less and in the early 19th century the castle was abandoned altogether. in 1873, the association for henneberg history and geography purchased the castle and began using it as a museum.