The district of Schwaz has been an administrative unit since 1868. The settlement and employment centres are located in the Inntal in the main district town of Schwaz, which became wealthy in the Middle Ages through its silver mines, and the market community of Jenbach. While the main valley is marked through its industry and is easily reachable, tourism plays an important role in the big side valleys of the Achental and the Zillertal which were once dominated by farming and which are isolated in their innermost regions. The Achensee Steam Rack-Railway runs from Jenbach to the Achental and to the southern tip of the Achensee. The lake that used to drain off naturally to the north into the Isar, now has water drawn from it in the south to supply the Achensee-Wasserkraftwerk hydro-electric power plant in Jenbach. The Zillertalbahn railway runs along the Zillertal as far as Mayrhofen. Reservoirs in the Zillertaler Alpen deliver the necessary water for the production of electricity in a number of power stations along the river Ziller. The Ziller also forms the boundary between the Diocese of Innsbruck and the Archdiocese of Salzburg. Among the biggest industrial firms in the district are the Jenbacher Werke, Darbo in Stans, Swarovski in Wattens, Alko-Kober in Zell am Ziller, the Adler-Werke in Schwaz and Derfeser in Vomp.