Berlin Wall - Wikipedia

On August 20, 1961" East Germany bagin erecting a 5' high wall along the border with the west to replace the barbed wire put up Aug 13. From the article:

"GDR authorities officially referred to the Berlin Wall as the Anti-Fascist Protection Rampart (German: Antifaschistischer Schutzwall). The West Berlin city government sometimes referred to it as the "Wall of Shame", a term coined by mayor Willy Brandt in reference to the Wall's restriction on freedom of movement.[5] Along with the separate and much longer Inner German border (IGB), which demarcated the border between East and West Germany, it came to symbolize physically the "Iron Curtain" that separated Western Europe and the Eastern Bloc during the Cold War.[6]

Before the Wall's erection, 3.5 million East Germans circumvented Eastern Bloc emigration restrictions and defected from the GDR, many by crossing over the border from East Berlin into West Berlin; from there they could then travel to West Germany and to other Western European countries. Between 1961 and 1989 the Wall prevented almost all such emigration.[7] During this period over 100,000[6] people attempted to escape and over 5,000 people succeeded in escaping over the Wall, with an estimated death toll ranging from 136[8] to more than 200[9][6] in and around Berlin.

In 1989 a series of revolutions in nearby Eastern Bloc countries—Poland and Hungary in particular—caused a chain reaction in East Germany that ultimately resulted in the demise of the Wall.[10] After several weeks of civil unrest, the East German government announced on 9 November 1989 that all GDR citizens could visit West Germany and West Berlin. Crowds of East Germans crossed and climbed onto the Wall, joined by West Germans on the other side in a celebratory atmosphere. Over the next few weeks, euphoric people and souvenir hunters chipped away parts of the Wall; the governments later used industrial equipment to remove most of what was left.[6] The "fall of the Berlin Wall" paved the way for German reunification, which formally took place on 3 October 1990."