 Up until 1920, the Marienwerder Region comprised the urban districts ("Stadtkreise") of Graudenz (Grudziądz) and Thorn (Toruń), both established on 1 January 1900.As a result of the Treaty of Versailles following World War I, most of West Prussia, including much of the Marienwerder Region, was allocated to the Second Polish Republic.Parts of the territory east of the river Vistula took part in the East Prussian plebiscite and remained in the Free State of Prussia within Weimar Germany.