Frankfurt

Holy Roman Empire de facto · 1789 – August 6, 1806 (from the border data)
Confederation of the Rhine de facto · April 11, 1807 – November 4, 1813 (from the border data)
German Confederation de facto · June 8, 1815 – May 18, 1848 (from the border data)
German Confederation de facto · November 29, 1850 – August 23, 1866 (from the border data)
Kingdom of Prussia de facto · October 1, 1866 – July 1, 1867 (from the border data)
North German Confederation de facto · July 1, 1867 – January 18, 1871 (from the border data)
German Empire de facto · January 19, 1871 – November 9, 1918 (from the border data)
Germany de facto · November 11, 1918 – May 8, 1945 (from the border data)
United States de facto · March 24, 1945 – May 8, 1945 Military occupation (from the border data)
Germany de facto · since May 23, 1949 (from the border data)

Confederation of the Rhine July 12, 1806 – November 4, 1813 From Wikidata (capital, P36)
German Confederation June 8, 1815 – August 24, 1866 From Wikidata (capital, P36)