Kennedy made his speech during a several-hour trip to West Berlin on June 26, 1963, nearly two years after communist East Germany cut the city in half by building the Berlin Wall and amid concern that America might abandon the Cold War outpost.
The "freedom bell" at the former West Berlin city hall, where Kennedy spoke to a crowd of some 300,000, tolled to mark today's anniversary ahead of a ceremony that featured students from Berlin's John F. Kennedy School reading excerpts from the speech in German and English.
"It matched the feelings, the hopes and the expectations of Berliners," Bahr said. "They knew instinctively, 'we can feel safe after this sentence.'"
Kennedy's declaration has become a symbol of strong German-U.S. Ties, and President Barack Obama evoked it when he spoke last week at the city's Brandenburg Gate, which in 1963 stood on the communist side of the wall.
Even today, "US presidents ... Can feel at home in this city," Berlin Mayor Klaus Wowereit said. Still, he alluded to the tensions that preceded Kennedy's euphoric reception.