The Peace of Westphalia ended religious warfare among the Imperial Estates; their mostly German-speaking rulers were able to choose Roman Catholicism, Lutheranism, or the Reformed faith as their official religion. The legal system initiated by a series of Imperial Reforms (approximately 1495–1555) provided for considerable local autonomy and a stronger Imperial Diet. The House of Habsburg held the imperial crown from 1438 until the death of Charles VI in 1740. Following the War of Austrian Succession and the Treaty of Aix-la-Chapelle, Charles VI's daughter Maria Theresa ruled as Empress Consort when her husband, Francis I, became Emperor.