In which year was the Wall in Berlin built?

EDITORIAL LEARNING AID

Why is this answer correct?

The Berlin Wall was built on 13 August 1961. 1953 was the year of the popular uprising in the GDR, and 1956 and 1959 were Cold War years without any wall being built. Only 1961 is therefore the correct year.

13 August 1961: the Wall goes up in Berlin.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.