Short answers, pulled from the story.
The Teutonic Knights constructed Memel Castle in 1252 where the Dangė river flows into the Neman River. This fortress marked a turning point in centuries of conflict between Baltic tribes and German crusaders.
Count Ulrich von Brockdorff-Rantzau led the German delegation at Paris Peace Conference who protested the decision on the 9th of May 1919. The Klaipėda Region appeared as a roughly-triangular wedge under the 1919 Treaty of Versailles while Allied Powers stated the district was always Lithuanian in origin and speech.
A Lithuanian census carried out in region during 1925 found total population was 141,000 people. Declared language classified inhabitants as 43.5 percent German, 27.6 percent Lithuanian, and 25.2 percent Klaipėdan.
On the 9th of January 1923, Lithuania occupied territory during the Klaipėda Revolt using militias entering from Lithuania itself. The Council of Ambassadors confirmed annexation by the 19th of February 1924 through a Convention signed in Paris.
Early hours of the 23rd of March 1939 saw oral ultimatum cause Lithuanian delegation travel to Berlin. Juozas Urbšys signed Treaty of Cession with Joachim von Ribbentrop exchanging territory for 99-year Free Zone in port while German forces seized territory even before official Lithuanian ratification occurred.
From 1945 to 1950 about 8,000 persons repatriated though bilingual returners viewed as Germans. In 1951 Lithuanian SSR expelled 3,500 people from former territory to East Germany.