AARGAU, a canton of north Switzerland, comprising the lower course of the River Aar (q.v.), whence its name. Its total area is 548sq.m. It forms the north-eastern section of the great Swiss plateau which occupies the trough between the Alps and the Jura. Its fertile valleys alternate with pleasantly-wooded hills.
In 1415 the Aargau region, previously the centre of the Habs burgs, was taken from them by the Swiss Confederates. Berne kept the south-west portion (Zofingen, Aarburg, Aarau, Lenz burg and Brugg), but some districts, named the Freie Amter or "free bailiwicks" (Mellingen, Muri, Villmergen and Bremgarten), with the county of Baden, were ruled as "subject lands" by all or certain of the Confederates. In 1798 the Bernese part became the canton of Aargau of the Helvetic republic, the remainder forming the canton of Baden. In 1803 the two halves (plus the Frick glen, ceded in 1802 by Austria to the Helvetic republic) were united under the name of Canton Aargau, which was then admit ted a full member of the reconstituted Confederation.
The population of the canton at the 1930 census was 259,644, almost exclusively German-speaking with Protestants predominat ing. The capital is Aarau (q.v.), while other towns are Baden, Zofingen, Reinach, Rheinfelden, Wohlen and Lenzburg. Aargau has profited from the exploitation of hydro-electric power. Silk ribbon weaving is an old industry and electro-technic production has been developed, while tobacco and wines are produced. There are extensive saline-springs at Rheinfelden, while Baden (q.v.) has a tourist industry dependent on its hot sulphur springs. The cantonal constitution dates mainly from 1885, but since 1904 the election of the executive council of five members is made by a direct vote. The canton sends 12 members (on the basis of the 1920 census) to the federal Nationalrat and two to the Standerat.