The empire was founded on 18 January 1871, when the south German states, except for Austria and Liechtenstein, joined the North German Confederation. The new constitution came into force on 16 April, changing the name of the federal state to the German Empire and introducing the title of German Emperor for Wilhelm I, King of Prussia from the House of Hohenzollern.[25] Berlin remained its capital, and Otto von Bismarck, Minister President of Prussia, became chancellor, the head of government. After 1850