 In year 1817, East Prussia had 796,204 Evangelical Christians, 120,123 Roman Catholics, 864 Mennonites and 2,389 Jews.From 1824–1878, East Prussia was combined with West Prussia to form the Province of Prussia, after which they were reestablished as separate provinces.Along with the rest of the Kingdom of Prussia, East Prussia became part of the German Empire during the unification of Germany in 1871.