This map shows the various areas of Germany in 1921.  For those just learning about Germany history,  it should be known to you that these areas were once German States and eached were ruled by powerful families.  Germany did not become one national unit until  1871.  Wilhelm I [House of Hohenzollern, which was the minor house of Brandenberg] became the Emperor. [Wilhelm I had been the King of Prussia.]  There was a Federal Diet (Reichstag) which held the Kingdoms of Prussia, Bavaria, Wuerttemberg and Saxony; the Grad Duchies of Baden, Hesse, Saxe-Weimer, Mecklenburg; and the lesser Principalities as well as the Hanseatic cities of Hamburg, Bremen and Luebeck.

List And Brief History of the German States, Grand Duchies, Principalities, etc.

Dates Important In German History