The eldest documented recount of Kleinwalsertal can be found in a certificate from 5 February 1059 stating that the emperor Heinrich IV gave a large hunting ground to the bishop Heinrich from Augsburg. Before the Walser’s immigration into Kleinwalsertal (1250-1300) both Tannberg and Mittelberg belonged to the barons of Rettenberg. This immigration took place about the same time as that of Tannberg explaining the long existing togetherness of the two municipalities. The barons allowed the clearing and settlement of those areas that had prior been used for hunting or as alps.

When the last male heir of the Rettenbergs died, Kleinwalsertal was given to Adelheid von Waldburg in 1350 who sold the estates to the Heimenhofen brothers the following year.

Tannberg and Mittelberg remained in the possession of this family for about hundred years. In 1451 lord Ulrich von Werdenber-Sargans and Hans von Rechberg (a robber-knight) came to the Tannberg because of some argument, exact reasons are unknown. Even though Duke Sigmund von Tirol had granted them safe conduct, the Walser captured and mistreated them. The duke asked for their release without having to pay but this was refused. Ulrich von Werdenberg was released but Hans von Rechberg remained captive. The duke conquered Tannberg with the force of arms whereupon all people in Tannberg, Lech, Zug, Berg, Gaisbühel, Schönenberg, Burstig, hohe Warth, Krummbach Älpele, Auenfeld, Mittelberg and Riezlern surrendered.
In 1563, Emperor Ferdinand separated the valley from the court Tannberg and set up the court Mittelberg. The valley’s three localities are combined to the political municipality, the “Gemeinde Mittelberg”.