Older Americans remember the day, 50 years ago, as the start of a darker, more cynical time. Many in the U.S. paused Friday to mark half a century since President John F. Kennedy's assassination.

The young, handsome president _ who created the Peace Corps, spoke at the Berlin Wall and challenged the country to go to the moon _ was shot dead while riding through Dallas, a conservative city that at times has struggled with the unwelcome fame of being forever ``linked in tragedy.''

``We watched the nightmarish reality in our front yard,'' Mayor Mike Rawlings told a crowd Friday. It was the first time the city had organized such a large event, issuing 5,000 free tickets. ``Our president had been taken from us, taken from his family, taken from the world.''

Two generations later, the assassination of a young leader still stirs quiet sadness in the baby boomer generation.

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.''

Rawlings' comments were followed by a tolling of bells and a moment of silence at the precise time that Kennedy was shot.

Drew Carney traveled from Toronto to attend the ceremony. The 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 compound in Massachusetts.

Shortly after sunrise, Attorney General Eric Holder paid his respects at Kennedy's recently refurbished grave at Arlington National Cemetery in Washington, where a British cavalry officer stood guard. 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.

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. (AP)