Short answers, pulled from the story.
The Free City of Danzig officially came into existence on the 15th of November 1920 under the protection of the League of Nations. This new state emerged from Article 100 of the Treaty of Versailles following World War I.
In 1910, the entire territory held 329,781 inhabitants with 312,358 being German-speakers and only 14,106 speaking Polish or Kashubian. Just 2,716 were Jews while a significant minority were Kashubs who formed another West Slavic group with their own identity.
Nazis won 50 percent of votes in the Volkstag elections of the Free City of Danzig in May 1933. Hermann Rauschning became President of the Senate of Danzig in June 1933 after this election result.
The battleship Schleswig-Holstein opened fire on Westerplatte at about 4:48am on the 1st of September 1939. This action fired the first shots of World War II from within the Free City of Danzig harbor.
By late 1945, between 10,000 and 15,000 pre-war inhabitants remained in the Free City of Danzig after an estimated 60,000 residents were expelled by Polish authorities. In December 1950, at least 85% of the population were post-war newcomers while over 10% were still pre-war Danzigers.