Between 1525 and 1809, Bad Mergentheim was the home of the Teutonic Knights, one of the most successful medieval orders of chivalry. In 1809, Napoléon expelled them as he marched toward his ill-fated Russian campaign. The expulsion seemed to sound the death knell of the little town, but in 1826 a shepherd discovered mineral springs on the north bank of the river. They proved to be the strongest sodium sulfate and
bitter spa waters in Europe, with supposedly health-giving properties that ensured the town's future prosperity as a health resort, which continues even today.