 In case of children born between September 1939 and December 1950, their origin was reported based on the pre-war places of residence of their mothers.Thanks to this data it is possible to reconstruct the pre-war geographical origin of the post-war population.The same area corresponding to pre-war southern parts of East Prussia (which became Polish in 1945) was inhabited in December 1950 by (this data includes the whole of Olsztyn Voivodeship as well as some counties of pre-1939 East Prussia which were incorporated to Białystok Voivodeship and to Gdańsk Voivodeship after World War II)