The Inn-Museum is Rosenheim's main local history museum, housed in a medieval toll house on the Inn riverbank. The collection centres on the salt trade that was Rosenheim's economic reason for existing: the town was a major transhipment point on the Inn, where salt from the mines at Bad Reichenhall and Berchtesgaden was loaded onto boats for the journey downriver.
The museum covers the history of salt extraction, river transport, and trade on the Inn from the medieval period through the early 20th century, when rail effectively ended the river trade. There are boat models, navigational instruments, and material on the craftsmen and bargemen who worked the river. It is modest in scale but gives a clear picture of why this particular stretch of river was important.