Posen was the southern of two Prussian administrative regions, or Regierungsbezirke (Polish: rejencja), of the Grand Duchy of Posen (1815–49) and its successor, the Province of Posen (1849–1918). The administrative region was bordered on the north by Regierungsbezirk Bromberg, to the west by the Province of Brandenburg, to the south by the Silesia Province, and to the east by Russian Congress Poland. The Posen region was inhabited mainly by Roman Catholic Poles, although it had a minority of mostly Protestant Germans. After World War I, most of the territory of this region was ceded to Poland.