After the end of World War I, in accordance with the terms of Article 100 (Section XI of Part III) of 1919 Treaty of Versailles was created The Free City of Gdansk (German: Freie Stadt Danzig, Polish: Wolne Miasto Gdańsk). The Free City of Gdansk was a city-state that existed between 1920-1939, consisting of the Baltic Sea port of Danzig (now Gdańsk, Poland) some 252 towns and villages and 63 hamlets, covering a total area of 1,966 square kilometers (759 sq mi).
The Free City was not autonomous. It was under League of Nations protection and put into a binding customs union with Poland, who had certain rights to the city. The Free City was created in order to give Poland access to a well-sized seaport, while at the same recognizing that its population was mainly German (population of 410,000 was 98% German, 1% Polish and 1% other). The official language was German, although the usage of Polish was guaranteed by law.