East German authorities began patrolling the inner-German border in 1952. Until then it had been relatively easy to pass between the two. They sealed off West Berlin in 1961. Here, soldiers keep people from crossing as the Berlin Wall is built.

In 1961, communist East Germany was having trouble keeping its young, educated population from emigrating to the West. The Berlin Wall was erected almost to completion in a single night, without warning, on August 13.

This famous photo from September 1961 shows a woman trying to escape East Berlin through an apartment block where one side of the building faced the West. Some men try to pull her back inside while others wait underneath, hoping to aid in her escape.

Amidst mounting internal and international pressure, a mistaken announcement by an East German official on November 9, 1989 led to the wall being opened. Germans on both sides of the border celebrated for days. New openings were made in the wall, like here at Potsdamer Platz two days later.

Today, some parts of the Berlin Wall still stand as a memorial to hard-won freedoms. The famous East Side Gallery allows different artists from around the world to add murals to the part of the wall that remains on Mühlenstrasse in Friedrichshain-Kreuzberg.

Politicians for the state government of Berlin lay flowers along the site of the Berlin Wall on Bernauer Strasse, 56 years to the day after it was constructed. At least 140 people were shot dead by East German border guards at the wall from 1961 to 1989.