West Berlin was the name of the western part of Berlin between 1949 and 1990. It was the American, British, and French occupied sectors that were created in 1945.
In many ways it was integrated (joined) with West Germany, but it was not a part of West Germany or East Germany. The Soviet sector became East Berlin, which East Germany claimed as its capital. The Western Allies never recognized this claim. They said that the whole city was still under four-power occupation. The building of the Berlin Wall in 1961 surrounded West Berlin.
These vintage postcards are of West Berlin from between the 1950s and ’70s.