There have been nine prior anniversary remembrances since the attacks, but this is the first one since al-Qaida mastermind Osama bin Laden was killed. And at those previous anniversaries, held at the temporary site, there were signs expressing hope that bin Laden would be hunted down.
On Sunday, though, his name was nowhere to be found on any sign or placard, and during both days of ceremonies, his name was never uttered, although during Mr. Obama's visit Sunday, one man in the crowd shouted: "Thank you for getting bin Laden."
Still, he was a barely discernible presence for at least one Flight 93 family member.
"At the time [of bin Laden's death] it certainly closed that chapter," said Gordon Felt, president of the Families of Flight 93. "To know he was no longer going to be involved in any more efforts to do terror is great but when I'm here, he's the last person I think about."
Paul Greengrass, the British writer, director and producer of the movie "United 93" that came out in 2006, flew to New York from London with his wife, Joanna, on Saturday and then got up and drove six hours to Somerset County to be there for Sunday's ceremony and help honor the families.
"It was the greatest privilege of my working life to make that film," said Mr. Greengrass, who also directed the last two Jason Bourne movies. "It was truly an honor."
He spent most of his time at the ceremony greeting family of the 40 passengers and crew, who seemed to treat him as another member of their larger family.
While some consider his acclaimed minute-by-minute movie about what happened on Flight 93 to be a memorial unto itself, Mr. Greengrass said the new permanent memorial is "incredibly moving and inspiring and beautiful."
"When the words are done, the [memorial's] stone and marble and natural forms designed for longevity will continue to speak about this story," he said.
The invocation was delivered by the Rev. Steven McKeown, an Episcopal priest from Aliquippa who is also an FBI chaplain.
In his prayer he spoke of a rainbow that appeared over the crash site, offering a sign of hope and encouragement to all of the first responders.
"Each one of them is now a part of the heavenly host," he said of the passengers and crew.
Mickey Odvar of Somerset wore a cap over her bald head and a surgical mask over her nose and mouth, concessions to the cancer she is battling. She didn't ask her doctor's permission to be among the crowd "and even if he said 'No,' I would have come anyway," she said.
Ten years ago she was an EMT working for a local manufacturing plant when the call came for every EMT in the region to report to the crash site. They were told to expect hundreds of victims.
"When we got here and started walking to the site we were told that it was just a hole. There were no people there," she said.
But the officers in charge asked the medical personnel to stay and form a human barrier to prevent anyone else from entering the crash site. So they did, standing six feet apart all day until busloads of police arrived to relieve them, she said.
"I've never been back for a memorial service. I'm here every year, but not on the anniversary," she said.
She came Sunday because "I hope and pray that everyone remembers and never forgets. As much as people in the United States want to believe we are untouchable, we aren't. We can never let our guard down."
Vicki Rock was seated in the media section, but she also was an invited guest, having covered the story of the flight and memorial from the beginning for the Somerset Daily American. She has developed relationships with the families and attended countless committee meetings.
But she had never been so close to the site of impact.
"When I came down the walkway and saw that, I knew they had got it right," she said.
A large boulder now rests like an altar among the wildflowers, marking the place of impact. On July 29 it replaced a flag, she said.
Construction workers building the road to the memorial had discovered the 17-ton stone, and were convinced it was the perfect natural monument, she said. But when they tried to move it using a chain rated for 20 tons, the chain broke three times.
Finally the National Parks superintendent told them to find a smaller stone, "but the construction firm said, 'No.' They had discovered this one, and they believed it was the right one. And they moved it," she said.
Such perseverance is a legacy of Flight 93, she said. It found echoes even in the inconveniences of the traffic backup that stalled many of Saturday's visitors. Ms. Rock was so concerned that she would miss the ceremony that she left the car in which she was riding and walked at least two miles to the site.
"As I was walking I passed an older man who was doing the same. And I was griping," she said. "He says, 'Think of the 40 heroes.' I said, 'You're right. I should be glad that I could walk in here and do this today."
Charles Wilkinson of Gallitzin, Cambria County, was one of many onlookers wearing Steelers jerseys. He had come with his two teenage sons, whom he has brought to the site many times.
"I felt it was important for them to be here today, to live the history," he said.
His older son, Jonathan, was surprised that former Gov. Tom Ridge and other politicians broke down as they recounted what transpired on Flight 93. "I liked that it wasn't just people talking about it, they were emotionally involved in it," he said.
His younger brother Jacob, 13, doesn't remember 9/11 and learned about it from their visits to the site.
"I learned that the people on the plane didn't care ... ," he stopped, struggling to find the right words.
"... about sacrificing their lives for others," his father finished for him as the boy nodded. "Usually when he talks about it, he gets very emotional about it," Mr. Wilkinson said.
Rita Schaier of Shaler first visited in April 2002. She had been moved by the serene natural beauty of the field, which was blooming with wildflowers.
"I knew that there would be a memorial here, and I hoped they didn't ruin it with a lot of hotels and buildings," she said.
"I'm so glad that they built it the way they did, with the wildflowers and trees, and without all the commercialization."
Carol Heiderich, an older sister of Flight 93 Capt. Jason Dahl, came to Sunday's ceremony with 45 family members and two pictures: one of Capt. Dahl in his United Airlines uniform; another of her brother Ken in his Army uniform.
Ken Dahl was just 20 when he died in 1971 serving in Vietnam.
"Ken's name is already on the Vietnam Memorial. And it struck me yesterday as they unveiled the names on the (memorial) wall that Jason's name is on a wall, too," she said.
There were dozens of uniformed airline flight attendants and pilots from United Airlines and other carriers who came out to the ceremonies Saturday and Sunday "to honor our fallen fellow crew members," said ExpressJet Capt. Chris Belcastro.
But some came with a more pointed agenda, American Airlines Capt. John Smith said on Saturday.
"We're just trying to show that the crews and airline employees don't get as much attention as they should," said Mr. Smith, who lives in York. "You just don't hear much about them, and it impacted our industry so much."
While some Flight 93 family members said Osama bin Laden's death didn't help them deal with their loss any better, Jerry Bingham, father of Flight 93 passenger Mark Bingham, said it did for him.
"To a certain point, it's a relief," he said. "But we definitely have a lot more [terrorists] out there we have to kill, too."
He said knowing the mastermind of 9/11 was still alive never weighed on him "because I had confidence our soldiers would get him."
Another regular visitor is Roger Dilling of Roaring Spring, Blair County, who came to the temporary memorial site -- since dismantled -- at least once a year since 9/11. Sunday's speakers were right when they said that the actions of the passengers and crew pose a moral challenge to every American, he said.
"Can you imagine the strength and the courage that it took for them to come together and react?" he said. "Could you do that? Could I do that? That's what sets us apart as Americans. We come out each year to see the memorial and remember that, day in and day out. We have to carry it on and teach our young the meaning of what happened here."
Celeste Calvitto was living 30 minutes from the Twin Towers on 9/11, but the Shanksville area means more to her, said the career journalist who now publishes a community newspaper in Bright, Ind.. Shanksville represents small-town America, she said.
She was present at the dedication not as a journalist but as a donor to the Flight 93 National Memorial. She gave because she believed it was crucial for the story to be remembered and taught.
"This really was the first battle of the war on terror," she said. "It's because they fought back and they were just ordinary people. They are us and we are them."
Sara Ianquinta, a senior at Connellsville Area High School, and Kaitlyn Hughes, in her first year at California University of Pennsylvania, are part of a volunteer group that sends care packages to U.S. soldiers. They visited the memorial on Sunday. Neither is old enough to have vivid memories of Sept. 11, but both are old enough to understand what the day now represents.
"I was only 8 at the time," said Kaitlyn. "I remember little things."
"It's ironic. Today the sky looks the same as it did 10 years ago," her friend Sara added.
Mark Givens drove in from Cleveland because "I wanted to do something special to honor [this] day."
He attended the dedication Saturday but said the most meaningful experiences he has had here were conversations with local people and members of the disaster mortuary team who worked here for weeks after the crash. Many of those professionals have returned every year on the anniversary, he added.
"What impressed me was how the local people have memories of this land when it was a strip mine and then a hunting ground. Now it honors the heroes and the initial effort to fight back against terrorism," he said.
Mary Blair, a flight attendant for United Airlines, knew one of the attendants on Flight 93. She said that although she's visited the Pittsburgh region in the past, this was the first time she's been to the crash site.
"We think about it when we're on the planes," she said. "It's a nice feeling to be here and know that they are safe and happy where they are now."