At the Potsdam Conference , northern Prussia , including Königsberg , was annexed by the USSR , regardless of whether the other powers had any say in the matter , which attached it to the Russian SFSR . In 1946 , the city 's name was changed to Kaliningrad . Northern Prussia remained part of the Soviet Union until its dissolution in 1991 , and since then has been an exclave of the Russian Federation
Potsdam Conference
Potsdam Conference
Königsberg