Silence filled the air at Dealey Plaza in Dallas, Texas, on Friday afternoon, as thousands descended on the spot where President John F. Kennedy was assassinated 50 years ago to pay tribute with flowers, candles, and song. Historian David McCullough remembered Kennedy with excerpts from some of the fallen president’s greatest speeches. “He knew words matter. His words changed lives. His words changed history. And rarely has a commander in chief addressed the nation with such command of language,” McCullough told the crowd. The invitation-only event held just 5,000 people, all picked through a special lottery.