Following World War I, the Allies included provisions within the Versailles Treaty which stripped Germany of of several of its territories. Among these was the city of Danzig (present-day Gdańsk, Poland).
Effective 15 November 1920, Danzig was designated the “Free City of Danzig” (in German, Freie Stadt Danzig), an autonomous region under the protection of the League of Nations. The “Free City” region consisted of the cities of Danzig and Zoppot (Sopot), and three rural districts — Danziger Höhe, Danziger Niederung, and Großes Werder
Danzig became a member of the Universal Postal Union on 1 October 1921. Early Danzig postage was created by overprinting German postage, but Danzig soon began issuing original designs, mostly featuring variations of the Danzig coat of arms.
With the start of World War II on 1 September 1939, Danzig was reintegrated into the Reich.