During World War II, it was occupied by Nazi Germany and unilaterally annexed as Reichsgau Danzig-Westpreußen ("Reich province of Danzig-West Prussia").

Poles and Jews were classified as untermenschen by German authorities and their intended fate slavery and extermination.

In 1945 out of its northern territory, the new voivodeship of Gdańsk was formed, including annexed territories of the Free City of Danzig and of German Prussian Province of Pomerania and German Prussian Province of East Prussia.

In the years 1975–1998, it was reorganized into the voivodeships of Gdańsk, Elbląg, Bydgoszcz, Toruń, and Włocławek.

With numerous cities and well-developed rail, it also provided the country with access to the Baltic Sea.