Alsace became a center of the Reformation (although the rural areas remained generally Catholic). The Treaty of Westphalia (1648) transferred all Hapsburg lands in Alsace to France. Lower Alsace was conquered (1680–97) by Louis XIV of France; the Treaty of Ryswick (1697) confirmed French possession. The Edict of Nantes (1685), promulgated before the annexation of Alsace, could not be revoked; therefore religious worship remained free. In 1798 the city of Mulhouse voted to join France.