In April 1946, northern East Prussia became an official province of the Russian SFSR as the "Kyonigsbergskaya Oblast", with the Memel Territory becoming part of the Lithuanian SSR. In June 1946 114,070 German and 41,029 Soviet citizens were registered in the Oblast, with an unknown number of disregarded unregistered persons. In July of that year, the historic city of Königsberg was renamed Kaliningrad to honour Mikhail Kalinin and the area named the Kaliningrad Oblast. Between 24 August and 26 October 1948 21 transports with in total 42,094 Germans left the Oblast to the Soviet Occupation Zone (which became East Germany). The last remaining Germans left in November 1949 (1,401 persons) and January 1950 (7 persons).

What year did East Prussia become an official province of Russia?