former province of Prussia, in NE Germany, on the Baltic Sea, separated from the rest of Germany (1919-39) by the Polish Corridor: in 1945, it was divided between Poland and the U.S.S.R.
See East Prussia in American Heritage Dictionary 4
A historical region and former province of Prussia on the Baltic Sea in present-day Poland and Russia. From 1919 to 1939 it was separated from Germany by the Polish Corridor. After World War II the area was divided between Poland and the USSR.