After World War II and the division of Germany, the eastern part of the nation became a Communist republic and adopted its own anthem to distinguish them from their western neighbour. This text is not as communist-oriented as several other communist anthems are, and also references a united Germany, perhaps because the anthem first started to be in use in the “Russian sector” of Germany before it was divided into East and West. Starting in 1971, the lyrics, while still official, were rarely sung at official occasions, perhaps because the Communist leaders noticed that this anthem does not really fit to their idea of an East German state, or because the unification of Germany, at least under communist rule, was becoming increasingly unlikely.
After the popular revolution in 1989 (the high point of which was the tearing down of the Berlin Wall), the lyrics came into favour again, and the “Deutchland einig Vaterland” notion was once again the slogan of East Germany. The words were once again used poularly until the union of the two Germanys, and the last East German parliament even attempted to make “Auferstanden aus Ruinen” the anthem of the united Germany, but this was refused by West Germany. Therefore, the anthem was official until East and West Germany united again in 1990 into a unified Germany. (In an interesting note, it was discovered after the fall of the Berlin Wall, when a new anthem for a unified Germany was being sought, that the words to “Auferstanden aus Ruinen” fit the melody of the “Deutchlandlied” (the anthem of then-West Germany) almost perfectly!)
Special thanks to: Ermano Geuer and Jan Scotland for some of this information, and Pavel Zinovatny for some additional information and the sheet music.