Frankfurt - Population of the 46 city districts on 31 December 2009

During the 1970s the state government of Hesse wanted to include the entire urban area into its administrative boundaries. This would have made Frankfurt officially the second largest city in Germany after Berlin with up to 3 million inhabitants.[21] However, because local authorities did not agree the administrative territory is still much smaller than its actual urban area.

Reference 1: Altstadt, Innenstadt, Bahnhofsviertel, Westend-Süd, Westend-Nord, Nordend-West, Nordend-Ost, Ostend, Bornheim, Gutleutviertel, Gallus, Bockenheim, Sachsenhausen-Nord, Sachsenhausen-Süd, Flughafen, Oberrad, Niederrad, Schwanheim, Griesheim, Rödelheim, Hausen, Praunheim, Heddernheim, Niederursel, Ginnheim, Dornbusch, Eschersheim, Eckenheim, Preungesheim, Bonames, Berkersheim, Riederwald, Seckbach, Fechenheim, Höchst, Nied, Sindlingen, Zeilsheim, Unterliederbach, Sossenheim, Nieder-Erlenbach, Kalbach-Riedberg, Harheim, Nieder-Eschbach, Bergen-Enkheim and Frankfurter Berg.

Reference 2: Population[24], Foreign nationals[24] and Area district (Ortsbezirk).

Source: http://en.wikipedia.org/wiki/Frankfurt_am_Main