The corn merchant and ship owner Joachim Rahlff (1756-1830) built the windmill in Lemkenhafen on Fehmarn in 1787. At this time the Fehmarn region was flourishing through commerce. Barley and wheat were ground to pearl barley and groats, which were exported to the Scandinavian countries. The groats mill was closed in 1953 and bought by the Land Schleswig-Holstein in 1957. It is under monumental protection as one of the oldest mills in Schleswig-Holstein. It was passed over to the “Verein zur Sammlung Fehmarnscher Altertümer” (association for the collection of antiquities on Fehmarn) in 1960. The association opened a museum in it in 1961. In addition to the building itself, the preserved grinding machinery and old corn measures are presented. From 1963 to 1965 the annexed storehouse was converted into a museum for farming implements. Models of farms on Fehmarn are also shown here.