In 1415, Frederick I became the elector of the Margraviate of Brandenburg, which he ruled until 1440. During the 15th century, his successors established Berlin-Cölln as capital of the margraviate, and subsequent members of the Hohenzollern family ruled in Berlin until 1918, first as electors of Brandenburg, then as kings of Prussia, and eventually as German emperors. In 1443, Frederick II Irontooth started the construction of a new royal palace in the twin city Berlin-Cölln. The protests of the town citizens against the building culminated in 1448, in the "Berlin Indignation" ("Berliner Unwille"). This protest was not successful and the citizenry lost many of its political and economic privileges. After the royal palace was finished in 1451, it gradually came into use. From 1470, with the new elector Albrecht III Achilles, Berlin-Cölln became the new royal residence. Officially, the Berlin-Cölln palace became permanent residence of the Brandenburg electors of the Hohenzollerns from 1486, when John Cicero came to power. Berlin-Cölln, however, had to give up its status as a free Hanseatic city. In 1539, the electors and the city officially became Lutheran.