At the Pentagon, 15,000 people turned out for the dedication of the first permanent memorial built at any of the three sites where hijacked planes crashed. It includes 184 benches that will glow at night, one for each victim there.
"Thanks to the brave men and women, and all those who work to keep us safe, there has not been another attack on our soil in 2,557 days," President Bush said at the outdoor dedication.
In New York, the crowd fell silent in a park just east of the trade center site at 8:46, 9:03, 9:59 and 10:29 a.m. - the times when two hijacked jets slammed into the buildings and the twin towers fell.
Alex, Aidan and Anna Salamone - now 13, 11 and 10 years old - wore old soccer jerseys belonging to their father, broker John Patrick Salamone, who was 37 when he was killed. They recalled playing in the yard with a toy wagon.
"He was strong. He was funny. He always made me laugh," Alex Salamone said. I wish I could remember more, but we were so young when he died."
"We love you, daddy," said Anna.
Still others chose to forgo the public observances altogether and mark the day in quieter, more private ways. Kai Thompson Hernandez toasted her late husband, Glenn Thompson, at a beach, with his favorite brand of beer.
"I try and celebrate his life rather than mark the place of his death," she said.
Family members of the trade center dead and students representing the more than 90 countries that lost citizens in the attack - from Azerbaijan to Zambia - read the names of the 2,751 victims killed in New York.
Others descended seven stories below street level to pay respects where the towers once stood. A giant crane, an American flag hanging from a hook, overlooked the anniversary ceremony from ground zero, where office towers, a memorial and transit hub are under construction.
The New York memorial is years away from completion. Some of the mourners worried the progress on it would prevent them from being allowed to pay respects next Sept. 11 on the ground where their loved ones died.
"When you walk through the site, you really feel like you're right where they were, and it's very raw," said Dennis Baxter, whose brother, Jasper, died while attending a conference at the trade center. "I think the spot should remain raw."
Many family members reading names paused to thank the troops fighting the two U.S. war launched since Sept. 11, 2001, drawing applause on several occasions.
"They took from us innocent lives in the names of their God," said Rosaria Reneo, whose sister Daniela R. Notaro was killed on Sept. 11, "and it seems some people have forgotten what happened here seven years ago."
Edward Bracken said to loud applause that his sister, Lucy A. Fishman, was "murdered by coward men using their religion to say they are right and we are wrong."
In Shanksville, Pa., McCain attended a simple ceremony held in a large field near the point where United Airlines Flight 93 slammed into the ground - driven down, investigators believe, when passengers who rushed the cockpit to prevent another attack on a building.
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. McCain said those on Flight 93 might have saved his own life. He said the only way to thank those who died on the flight is to "be as good an American as they were."
"We might fall well short of their standard, but there's honor in the effort," the Republican Arizona senator said.
Obama, in a statement, recalled that after the attacks, "Americans across our great country came together to stand with the families of the victims, to donate blood, to give to charity, and to say a prayer for our country. Let us renew that."
In New York, relatives of victims began arriving at dawn for the memorials, wearing their loved ones' pictures on T-shirts and holding signs saying, "We miss you," "We love you" or "You will never be forgotten."
As in years past, two bright blue beams of light rose from lower Manhattan in memory of the fallen towers. But many family members said they wished there were more of a memorial.
"It's still very hard for us to come here. It doesn't get any easier," said Norma Linguito, a relative of Sept. 11 victim Michael Diehl. "I just wish they'd get the memorial up so we can have something, a marker, to remember everyone."
