Three American presidents stood somberly side by side Saturday at the National September 11 Memorial in New York, sharing a moment of silence to mark the anniversary of the nation's worst terrorist attack with a display of unity.Presidents Joe Biden, Barack Obama and Bill Clinton gathered at the site where the World Trade Center towers fell two decades ago. Each man wore a blue ribbon and held his hands over his heart as a procession marched a flag through the memorial before hundreds of people, some carrying photos of loved ones lost in the attacks. Before the event began, a jet flew overhead in an eerie echo of the attacks, drawing a glance from Biden toward the sky. For much of the ceremony he stood with his arms crossed and head bowed, listening while the names of the victims were read. At one point, he wiped a tear from his eye.Biden was a senator when hijackers commandeered four planes and carried out the attack. He was Obama's vice president in 2011 when the country observed the 10th anniversary of the strikes. Saturday's commemoration was his first as commander in chief, beginning in New York City and culminating late afternoon at the Pentagon, where the world's mightiest military suffered an unthinkable blow to its very home. In between he visited Shanksville, Pennsylvania, where passengers brought down a hijacked plane that was headed for the U.S. Capitol. Biden and his wife, Jill, walked with relatives of the crash victims into the grassy field where the jet came to rest. He reflected on the need for unity when he dropped by the Shanksville Volunteer Fire Department to deliver Bud Light and thank first responders who responded to the plane crash on Sept. 11."Everyone says Biden, 'Why do you keep insisting on trying to bring the country together?'' the president told reporters. "That's the thing that's going to affect our well-being more than anything else."It is now Biden who shoulders the responsibility borne by his predecessors to prevent another strike. He must do that against fears of a rise in terrorism after the hasty U.S. withdrawal from Afghanistan, where those who planned the Sept. 11 attacks were sheltered. But on a day when his nation recalled its shock and sorrow, Biden left the speech-making to others.Biden's vice president, Kamala Harris, spoke in Shanksville at the Flight 93 National Memorial, praising the courage of those passengers and the resilience of Americans who came together in the days after the attacks. "In a time of outright terror, we turned toward each other," she said. "If we do the hard work of working together as Americans, if we remain united in purpose, we will be prepared for whatever comes next."Former President George W. Bush, speaking before Harris, recalled how 9/11 showed that Americans could unite despite their differences. It was a message, he said, that was needed today. "So much of our politics have become a naked appeal to anger, fear and resentment," Bush said. "On America's day of trial and grief, I saw millions of people instinctively grab for a neighbor's hand, and rally for the cause of one another. That is the America I know."Biden, speaking at the firehouse later, praised Bush's message of unity, and mentioned that he had taken photos with some boys wearing Trump hats at the firehouse. Biden framed the need for unity as a crucial to the success of democracies, asking "Are we going to, in the next four, five, six, 10 years, demonstrate that democracies can work, or not?"Former President Donald Trump skipped the official 9/11 memorial ceremonies and instead visited a fire station and police precinct in New York.While Biden had no prepared remarks of his own Saturday, he did offer praise for Bush's words, telling reporters in Pennsylvania that he thought the former president "made a really good speech today. Genuinely."But unity was a theme that Biden emphasized in a taped address released by the White House late Friday. He spoke about the "true sense of national unity" that emerged after the attacks, seen in "heroism everywhere — in places expected and unexpected.""To me that's the central lesson of September 11," he said. "Unity is our greatest strength."Biden is the fourth president to console the nation on the anniversary of that dark day, one that has shaped many of the most consequential domestic and foreign policy decisions made by the chief executives over the past two decades. Bush was reading a book to Florida schoolchildren when the planes slammed into the World Trade Center. He spent that day being kept out of Washington for security reasons — a decision then-Sen. Biden urged him to reconsider, the current president has written — and then delivered a brief, halting speech that night from the White House to a terrified nation.The terrorist attack would define Bush's presidency. The following year, he chose Ellis Island as the location to deliver his first anniversary address, the Statue of Liberty over his shoulder as he pledged, "What our enemies have begun, we will finish."The wars in Iraq and Afghanistan were still deadly when Obama visited the Pentagon to mark his first Sept. 11 in office in 2009. By the time Obama spoke at the 10th anniversary, attack mastermind Osama bin Laden was dead, killed in a May 2011 Navy SEAL raid. Though the nation remained entangled overseas, and vigilant against terrorist threats, the anniversary became more about healing. "We reaffirm our commitment to keep a sacred trust with their families — including the children who lost parents, and who have demonstrated such extraordinary resilience. But this anniversary is also about reflecting on what we've learned in the 20 years since that awful morning," Obama said in a statement early Saturday morning."That list of lessons is long and growing. But one thing that became clear on 9/11 — and has been clear ever since — is that America has always been home to heroes who run towards danger in order to do what is right."When they think back on Sept. 11, 2001, Obama said, he and former First Lady Michelle Obama aren't left only with lasting images of two planes flying into the twin towers of the World Trade Center or the wreckage at the other attack sites, but also with the courage of the first responders who acted on that day and in the following weeks and months."It's the firefighters running up the stairs as others were running down. The passengers deciding to storm a cockpit, knowing it could be their final act. The volunteers showing up at recruiters' offices across the country in the days that followed, willing to put their lives on the line," the former president wrote.That same selflessness, Obama said, has been on display "again and again" over the past two decades.

Three American presidents stood somberly side by side Saturday at the National September 11 Memorial in New York, sharing a moment of silence to mark the anniversary of the nation's worst terrorist attack with a display of unity.

Presidents Joe Biden, Barack Obama and Bill Clinton gathered at the site where the World Trade Center towers fell two decades ago. Each man wore a blue ribbon and held his hands over his heart as a procession marched a flag through the memorial before hundreds of people, some carrying photos of loved ones lost in the attacks.

Before the event began, a jet flew overhead in an eerie echo of the attacks, drawing a glance from Biden toward the sky. For much of the ceremony he stood with his arms crossed and head bowed, listening while the names of the victims were read. At one point, he wiped a tear from his eye.

Biden was a senator when hijackers commandeered four planes and carried out the attack. He was Obama's vice president in 2011 when the country observed the 10th anniversary of the strikes. Saturday's commemoration was his first as commander in chief, beginning in New York City and culminating late afternoon at the Pentagon, where the world's mightiest military suffered an unthinkable blow to its very home.

Chip Somodevilla/Pool Photo via AP

In between he visited Shanksville, Pennsylvania, where passengers brought down a hijacked plane that was headed for the U.S. Capitol. Biden and his wife, Jill, walked with relatives of the crash victims into the grassy field where the jet came to rest.

He reflected on the need for unity when he dropped by the Shanksville Volunteer Fire Department to deliver Bud Light and thank first responders who responded to the plane crash on Sept. 11.

"Everyone says Biden, 'Why do you keep insisting on trying to bring the country together?'' the president told reporters. "That's the thing that's going to affect our well-being more than anything else."

It is now Biden who shoulders the responsibility borne by his predecessors to prevent another strike. He must do that against fears of a rise in terrorism after the hasty U.S. withdrawal from Afghanistan, where those who planned the Sept. 11 attacks were sheltered.

But on a day when his nation recalled its shock and sorrow, Biden left the speech-making to others.

Biden's vice president, Kamala Harris, spoke in Shanksville at the Flight 93 National Memorial, praising the courage of those passengers and the resilience of Americans who came together in the days after the attacks.

"In a time of outright terror, we turned toward each other," she said. "If we do the hard work of working together as Americans, if we remain united in purpose, we will be prepared for whatever comes next."

Former President George W. Bush, speaking before Harris, recalled how 9/11 showed that Americans could unite despite their differences. It was a message, he said, that was needed today.

"So much of our politics have become a naked appeal to anger, fear and resentment," Bush said. "On America's day of trial and grief, I saw millions of people instinctively grab for a neighbor's hand, and rally for the cause of one another. That is the America I know."

Biden, speaking at the firehouse later, praised Bush's message of unity, and mentioned that he had taken photos with some boys wearing Trump hats at the firehouse. Biden framed the need for unity as a crucial to the success of democracies, asking "Are we going to, in the next four, five, six, 10 years, demonstrate that democracies can work, or not?"

Former President Donald Trump skipped the official 9/11 memorial ceremonies and instead visited a fire station and police precinct in New York.

While Biden had no prepared remarks of his own Saturday, he did offer praise for Bush's words, telling reporters in Pennsylvania that he thought the former president "made a really good speech today. Genuinely."

But unity was a theme that Biden emphasized in a taped address released by the White House late Friday. He spoke about the "true sense of national unity" that emerged after the attacks, seen in "heroism everywhere — in places expected and unexpected."

"To me that's the central lesson of September 11," he said. "Unity is our greatest strength."

Biden is the fourth president to console the nation on the anniversary of that dark day, one that has shaped many of the most consequential domestic and foreign policy decisions made by the chief executives over the past two decades.

Bush was reading a book to Florida schoolchildren when the planes slammed into the World Trade Center. He spent that day being kept out of Washington for security reasons — a decision then-Sen. Biden urged him to reconsider, the current president has written — and then delivered a brief, halting speech that night from the White House to a terrified nation.

The terrorist attack would define Bush's presidency. The following year, he chose Ellis Island as the location to deliver his first anniversary address, the Statue of Liberty over his shoulder as he pledged, "What our enemies have begun, we will finish."

The wars in Iraq and Afghanistan were still deadly when Obama visited the Pentagon to mark his first Sept. 11 in office in 2009.

By the time Obama spoke at the 10th anniversary, attack mastermind Osama bin Laden was dead, killed in a May 2011 Navy SEAL raid. Though the nation remained entangled overseas, and vigilant against terrorist threats, the anniversary became more about healing.

"We reaffirm our commitment to keep a sacred trust with their families — including the children who lost parents, and who have demonstrated such extraordinary resilience. But this anniversary is also about reflecting on what we've learned in the 20 years since that awful morning," Obama said in a statement early Saturday morning.

"That list of lessons is long and growing. But one thing that became clear on 9/11 — and has been clear ever since — is that America has always been home to heroes who run towards danger in order to do what is right."

When they think back on Sept. 11, 2001, Obama said, he and former First Lady Michelle Obama aren't left only with lasting images of two planes flying into the twin towers of the World Trade Center or the wreckage at the other attack sites, but also with the courage of the first responders who acted on that day and in the following weeks and months.

"It's the firefighters running up the stairs as others were running down. The passengers deciding to storm a cockpit, knowing it could be their final act. The volunteers showing up at recruiters' offices across the country in the days that followed, willing to put their lives on the line," the former president wrote.

That same selflessness, Obama said, has been on display "again and again" over the past two decades.

For John Wesley, no day has a greater significance than Sept. 11, 2001. His reasons are deeply personal, powerful and inspiring.Images of his fiancée are indelibly etched in Wesley's mind, heart and soul. Sarah Clark died when terrorists hijacked American Airlines Flight 77 and deliberately crashed into the Pentagon."She saw the same old world each day with new eyes, and her compassion never blinks," Wesley said.Authorities allowed Wesley to watch the boarding gate video. He saw two of the hijackers looking at a child playing with an Elmo toy, seniors being pushed onboard in wheelchairs and students securing their backpacks."For me, how could you look at that and still do what was on your mind?" Wesley said.Wesley decided at the last minute not to go on the trip with Clark because it was his first day on the job as an actor on HBO'S "The Wire.""Growing up in Mississippi, I just believe I would have fought," Wesley said.Every year on the 9/11 anniversary, Wesley visits the Pentagon crash site. He will be there this year, as well. In 2018, former Vice President Mike Pence mentioned Clark in his remarks. Wesley said her positive influence has made him a better man. He said she helped lead him back to his faith."People need help. People need compassion. And I wanted people to know that I had no malice, that I never asked God why. I just thanked him for the time that I had with her and all the things that happened with her," Wesley said.Clark taught sixth grade at Backus Middle School in Washington, D.C. She was on Flight 77 to chaperone students to an ecology conference sponsored by National Geographic.Days before the flight, Wesley and Clark decided to bump up their wedding date to December. They picked a place to hold their wedding reception and shopped for wedding bands.Wesley had the grim task of identifying Clark's remains."I was looking for this ring because this is the ring she would have had on," Wesley said. Wesley said that over the years, he has focused on writing music and books inspired by Clark."If we are going to stop this hatred, we are going to have to start with the children," Wesley said. "That's the real lesson, and that will be our saving grace if we learn to love each other."Wesley has since found a new love, which he said has helped him emotionally. His work in the Baltimore City Office of Civil Rights is his passion."It seems I am where I'm supposed to be," Wesley said.Wesley has advice for anyone who has suddenly lost a loved one, saying life is short, to honor them by doing a simple act of kindness and use that depth of pain to lift others up.