But 50 years later, the thousands of people who filled Dealey Plaza weren't there to cheer but to remember in quiet sadness the young, handsome president with whom Dallas will always be "linked in tragedy."
The solemn ceremony presided over by Mayor Mike Rawlings was the first time the city had organized an official Kennedy anniversary event, issuing 5,000 free tickets and erecting a stage with video screens.
Somber remembrances extended from Dallas to the shores of Cape Cod, with moments of silence, speeches by historians and, above all, simple reverence for a time and a leader long gone.
"We watched the nightmarish reality in our front yard," Rawlings told the crowd, which assembled just steps from the Texas School Book Depository building where Lee Harvey Oswald fired from the sixth floor at Kennedy's open-top limousine. "Our president had been taken from us, taken from his family, taken from the world."
Two generations later, the assassination still stirs quiet sadness in the baby boomers who remember it as the beginning of a darker, more cynical time.
"A new era dawned and another waned a half-century ago, when hope and hatred collided right here in Dallas," Rawlings told the crowd that gathered under gray skies and in near-freezing temperatures. The mayor said the slaying prompted Dallas to "turn civic heartbreak into hard work" and helped the city mature into a more tolerant, welcoming metropolis.
The slain president "and our city will forever be linked in tragedy, yes," Rawlings said. "But out of tragedy, an opportunity was granted to us: how to face the future when it's the darkest and uncertain."
Historian David McCullough said Kennedy "spoke to us in that now-distant time past, with a vitality and sense of purpose such as we had never heard before."
Kennedy "was young to be president, but it didn't seem so if you were younger still," McCullough added. "He was ambitious to make it a better world, and so were we."
Past anniversaries in Dealey Plaza have been marked mostly by loose gatherings of the curious and conspiracy-minded, featuring everything from makeshift memorials and marching drummers to freewheeling discussions about others who might have been in on the killing.
On Friday, the mayor unveiled a plaque with remarks the president was supposed to deliver later that day in Dallas. Rawlings' comments were followed by a mournful tolling of bells and a moment of silence at the precise time that Kennedy was shot.
In Dallas, the dreary weather was far different from the bright sunshine that filled the day of the assassination. But that didn't stop crowds from lining up hours before the ceremonies began.
Drew Carney and his girlfriend, Chelsea Medwechuk traveled from Toronto to attend the ceremony. Like many of those in attendance, they wore plastic ponchos to ward off the rain.
At 25 and 24, respectively, they were born a quarter-century after Kennedy died. Carney, a high school history teacher, said he became intrigued with Kennedy and his ideals as a teenager.
"It filled you with such hope," he said.
Elsewhere, flags were lowered to half-staff and wreaths were laid at Kennedy's presidential library and at a waterfront memorial near the family's Cape Cod compound.
Shortly after sunrise, Attorney General Eric Holder paid his respects at Kennedy's recently refurbished grave at Arlington National Cemetery, where a British cavalry officer stood guard, bagpipes played and a flame burned steadily as it has since Kennedy was buried.
About an hour later, Jean Kennedy Smith, 85, the last surviving Kennedy sibling, laid a wreath at her brother's grave, joined by about 10 members of the Kennedy family. They clasped hands for a short, silent prayer and left roses as a few hundred onlookers watched.
In Boston, Gov. Deval Patrick and Maj. Gen. Scott Rice of the Massachusetts National Guard endured a heavy rain during a wreath-laying ceremony at the Kennedy statue on the front lawn of the Statehouse. The statue, dedicated in 1990, has been largely off-limits to public viewing since security procedures put in place after the 9/11 terrorist attacks. But the area was opened to visitors Friday.
Both of Kennedy's grandfathers served in the Massachusetts Legislature, and in January 1961 the president-elect came to the Statehouse to deliver one of his most famous addresses, which came to be known as the "City on a Hill" speech, just before leaving for his inauguration in Washington.
The tributes extended across the Atlantic to Kennedy's ancestral home in Ireland.
In Dublin, a half-dozen Irish soldiers toting guns with brilliantly polished bayonets formed an honor guard outside the U.S. Embassy as the American flag was lowered to half-staff. An Irish army commander at the embassy drew a sword and held it aloft as a lone trumpeter played "The Last Post," the traditional British salute to war dead.
More than a dozen retired Irish army officers who, as teenage cadets, had formed an honor guard at Kennedy's graveside gathered in the front garden of the embassy to remember the first Irish-American to become leader of the free world.
Together with Irish Foreign Minister Eamon Gilmore and embassy staff, they observed a moment of silence and laid wreaths from the Irish and American governments in JFK's memory.
Associated Press writers Bob Salsberg in Boston, Matthew Barakat in Washington and Shawn Pogatchnik in Dublin contributed to this report.