The nation paused to mark the seventh anniversary of Sept. 11 on Thursday, holding ceremonies and moments of silence to commemorate the terrorist attacks that killed nearly 3,000.
President Bush led a White House gathering, while relatives of victims killed in New York City did the same in downtown Manhattan.
Other ceremonies were held throughout the day, including one at the Pentagon, where 15,000 people turned out for the dedication of the first permanent memorial built in remembrance of 9/11. It includes 184 benches that will glow at night, one for each victim there.
"Today marks the seventh anniversary of the day our world was broken," Mayor Michael Bloomberg said in New York City. "It lives forever in our hearts and our history, a tragedy that unites us in a common memory and a common story ... the day that began like any other and ended as none ever has."
In lower Manhattan, family members and students representing more than 90 countries that lost citizens on Sept. 11 read the names of the more than 2,700 people killed in New York.
The ceremony at ground zero included moments of silence at 8:46 a.m. and 9:03 a.m., the times that two hijacked jets slammed into the World Trade Center in New York. Another was flown into the Pentagon and another crashed in a field in Shanksville, Pa.
Two more moments of silence were held at the times the towers fell.
At the White House, scores of invited guests and staff people joined Bush in observing the anniversary.
Standing next to the president under threatening skies for the brief South Lawn ceremony were his wife, Laura, and Vice President Dick Cheney and his wife, Lynne. A chorus sang "God Bless America."
The assembled crowd numbered in the hundreds and included leaders of Congress, members of the Cabinet, diplomats, men and women in military uniform and chefs, plumbers, ushers and others who work at the White House.
Across the Potomac River, a new memorial to those killed at the Pentagon was dedicated as the names of the victims were read aloud to mourners there.
Presidential candidates John McCain and Barack Obama paid silent respects at ground zero Thursday afternoon and later attended a forum on public service, held at Columbia University.
McCain also attended a memorial service in Shanksville for the 40 people killed aboard United Airlines Flight 93. Grieving family members and a few dignitaries sat in front of a chain-link fence adorned with flags and mementos that serves as a temporary memorial while a permanent one is constructed. Bells rang as the name of each victim was read.
In New York, some mourners wondered if the remembrance would, or should, continue as it has indefinitely. About 3,500 people attended last year's ceremony, a roughly 25 percent decrease from 2006.
"We've kept it alive, and perhaps kept it alive too long," said Charles Wolf, whose wife, Katherine, was killed at the World Trade Center. "How many times do you reopen the wounds?"
Wolf, who lives in downtown Manhattan, attends the ceremony every year but said it has become more painful, especially to stand in silence for the moment that the plane crashed into the tower where his wife worked. "It's one thing to remember," he said, "but it's another to relive it."
Other victims' relatives worry that Sept. 11 will revert to being just another date on the calendar.
"The remembrances have to continue; for how long, I can't say," said Barbara Minervino of Middletown, N.J., whose husband, Louis, died in the twin towers. "But we have to memorialize the fact that this day happened in the history of the United States and the history of the world. The day we forget, then why are we living?"
Minervino attended a noon Mass in her husband's memory after listening to the names being read during the memorial service in New York.
That service moved to a park just east of ground zero last year because of construction at the trade center site. But family members were allowed to descend seven stories below ground and touch the spot where their loved ones died.
The ceremony included the reading of 2,751 victims' names, one more than last year. The city restored Sneha Philip, a woman who vanished on Sept. 10, to its official death toll this year after a court ruled that she was likely killed at the trade center.
Former Mayor Rudy Giuliani spoke at the ceremony, as he has every year, along with Bloomberg and Homeland Security Secretary Michael Chertoff.
Last year's reading by Giuliani, then a Republican presidential candidate, drew protests from family members who said the city was ill-prepared for the terrorist attacks under his leadership and questioned whether he should be there while running for the White House. They had no opposition to McCain and Obama visiting this year.
Memorials are years away from being built in Pennsylvania and New York. The stalled, complex rebuilding of office towers, a transit station and memorial at ground zero led New York Gov. David Paterson to order a reevaluation of budgets and schedules for all projects. The Lower Manhattan Development Corp., the agency that owns the site, has said the planned 8-acre memorial might not completed by the 10th anniversary of the attacks.