Müllheim is first mentioned in 1254 as "Mulhain". In the 13th and 14th Centuries the Ministerialis (unfree knights in the service of a feudal overlord) family of Müllheim was mentioned. Initially the Counts of Kyburg owned the bailiwick of Müllheim. When that line died out, the Habsburgs took over. Reichenau Abbey bought the rights over the village in 1460. The abbey and its successors (between 1540-1798 the Bishop of Constance) were the judicial rulers and landlords of the village. The municipality had the right to impose fines and light corporal punishment