The Margraviate of Brandenburg was the core province of the Prussian monarchy until 1815. This map shows its division into administrative units or districts. In the seventeenth and eighteenth centuries, Brandenburg was a sparsely populated, mostly rural territory whose main centers of settlement had grown along the major rivers Elbe, Spree, Oder and Netze. The Cottbus district formed an enclave separated from the margraviate’s main territory after the Brandenburg Elector Frederick II acquired the territory in the fifteenth century. In addition to the princely (and after 1701 royal) seat Berlin, the most important towns included Potsdam, Spandau, Stendal, Prenzlau, Frankfurt an der Oder and Cüstrin (today: Kostrzyn nad Odrą in Poland).