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MANHATTAN — Americans solemnly marked the 20th anniversary of 9/11 on Saturday, remembering the deadliest terror attack on U.S. soil just weeks after the fraught end of the Afghanistan war that followed.
With a tolling bell and a moment of silence, the anniversary ceremony at ground zero in New York began exactly two decades after the attack started with the first of four hijacked planes crashing into one of the World Trade Center’s twin towers.
New York police and firefighters hold a US flag at the National 9/11 Memorial during a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
New York police and firefighters hold a US flag as a band plays the US National Anthem at the National 9/11 Memorial during a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. – A solemn ceremony to mark the 20th anniversary of the 9/11 attacks on the United States got under way in New York on Saturday under tight security. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
Katie Mascali is comforted by her fiance Andre Jabban as they stand near the name of her father Joseph Mascali during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. (Photo by Craig Ruttle / POOL / AFP) (Photo by CRAIG RUTTLE/POOL/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A member of the FDNY visits the reflecting pool during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: (L-R) Former President Bill Clinton, former First Lady Hillary Clinton, former President Barack Obama, former First Lady Michelle Obama, President Joe Biden, First Lady Jill Biden, former New York City Mayor Michael Bloomberg, Bloomberg’s partner Diana Taylor, Speaker of the House Nancy Pelosi (D-CA) and Senate Minority Leader Charles Schumer (D-NY) stand for the national anthem during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family members and friends of New York City Police Department Detective Joseph Paolillo and Fire Department City of New York Deputy Chief John Paolillo visit the memorial before a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: New York police and firefighters hold a U.S. flag as a band plays the U.S. National Anthem at the National 9/11 Memorial during a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Ed Jones-Pool/Getty Images) 
New York City Mayor Bill de Blasio (L) and Former New York City Mayor Rudy Giuliani (R) attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: The photo of a 9/11 victim is carried by family and friends as they attend a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Ed Jones-Pool/Getty Images) 
A fireman holds up the image of a 9/11 victim as people attend a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
TOPSHOT – US President Joe Biden (R), former US President Barack Obama(L), and former First Lady Michelle Obama (C) attend a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. – A solemn ceremony to mark the 20th anniversary of the 9/11 attacks on the United States got under way in New York on Saturday under tight security. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: The photo of a 9/11 victim is carried by family and friends as they attend a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Ed Jones-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Bruce Springsteen performs during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
Former first lady Michelle Obama, President Joe Biden and first lady Jill Biden attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci) 
NEW YORK, NEW YORK – SEPTEMBER 11: A woman places flowers on the 9/11 Memorial before a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family members and loved one of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: The photo of a 9/11 victim is carried by family and friends as they attend a ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Ed Jones-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A man mourns at the 9/11 Memorial on the 20th anniversary of the September 11 attacks in Manhattan, New York City, U.S., September 11, 2021. REUTERS/Mike Segar during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family members of Jayesh Shah make a rubbing of his name at the 9/11 Memorial before a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Retired Willow Springs, IL Chief Sam Pulia and his nephew, Chicago Police Sgt. Daniel Pulia place flags at the South Tower before a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by David Handschuh-Pool/Getty Images) 
The photos of 9/11 victims are carried by family and friends as they attend a ceremony at the National 9/11 Memorial & Museum commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by ED JONES / POOL / AFP) (Photo by ED JONES/POOL/AFP via Getty Images) 
A bell is rung during a moment of silence during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by Chip Somodevilla / POOL / Getty Images) (Photo by CHIP SOMODEVILLA/POOL/AFP via Getty Images) 
Joe Walker, a man who lives in the neighborhood, wipes a tear from his face as he participates in the 20th anniversary of the 9/11 attacks on the World Trade Center near the 9/11 Memorial & Museum in New York, on September 11, 2021. – America marked the 20th anniversary of 9/11 Saturday with solemn ceremonies given added poignancy by the recent chaotic withdrawal of troops from Afghanistan and return to power of the Taliban. (Photo by ROBERTO SCHMIDT / AFP) (Photo by ROBERTO SCHMIDT/AFP via Getty Images) 
Family members and loved one of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by Chip Somodevilla / POOL / Getty Images) (Photo by CHIP SOMODEVILLA/POOL/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Melinda Moran and Haydee Lillo embrace after finding out they lost people who knew each other, next to the North Reflecting Pool during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: People visit the 9/11 Memorial during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: People embrace at the 9/11 Memorial during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
A couple embrace near ceremonies for the 20th anniversary of the 9/11 attacks on the World Trade Center near the 9/11 Memorial & Museum in New York, on September 11, 2021. – America marked the 20th anniversary of 9/11 Saturday with solemn ceremonies given added poignancy by the recent chaotic withdrawal of troops from Afghanistan and return to power of the Taliban. (Photo by ROBERTO SCHMIDT / AFP) (Photo by ROBERTO SCHMIDT/AFP via Getty Images) 
(L-R) Former President Barack Obama, former First Lady Michelle Obama, President Joe Biden, First Lady Jill Biden and former New York City Mayor Michael Bloomberg attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by Chip Somodevilla / POOL / Getty Images) (Photo by CHIP SOMODEVILLA/POOL/AFP via Getty Images) 
Family members and loved one of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by Chip Somodevilla / POOL / Getty Images) (Photo by CHIP SOMODEVILLA/POOL/AFP via Getty Images) 
Family members and loved ones of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by David Handschuh / POOL / Getty Images) (Photo by DAVID HANDSCHUH/POOL/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Randall Goosby (R) and pianist Zhu Wang perform during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A family member of Jennie Nicole Gonzalez attends the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Chris Jackson performs during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A photo, flags and flowers adorn the National 9/11 Memorial and Museum during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Ed Jones-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: People mourn at the North reflecting pool during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family members and loved ones of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
People react as they attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci) 
People react as they attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci) 
NEW YORK, NEW YORK – SEPTEMBER 11: People attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
A tree is adorned with photos of victims, a flag and flowers the National 9/11 Memorial and Museum during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Ed JONES / AFP) (Photo by ED JONES/AFP via Getty Images) 
A man holds a US flag outside “Freedom Tower” (C, rear) during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Ed JONES / AFP) (Photo by ED JONES/AFP via Getty Images) 
Family member grieve at the National 9/11 Memorial during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Ed JONES / AFP) (Photo by ED JONES/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A tribute to Black firefighters is seen during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: The photo of a loved one is raised as the names of victims are read during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family members and loved ones of Stuart Todd Meltzer attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A man with his daughter on his shoulders looks on at the north reflecting pool during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: A woman places flowers as she visits the 9/11 Memorial during a ceremony at the National September 11 Memorial & Museum commemorating the 20th anniversary of the September 11th terrorist attacks on the World Trade Center on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA, and the Pentagon, killing nearly 3,000 people. (Photo by Mike Segar-Pool/Getty Images) 
A family member grieves at the National 9/11 Memorial and Museum ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by ED JONES / POOL / AFP) (Photo by ED JONES/POOL/AFP via Getty Images) 
Family members and loved ones of victims attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York. (Photo by Chip Somodevilla / POOL / Getty Images) (Photo by CHIP SOMODEVILLA/POOL/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: People attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: People attend the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
US President Joe Biden (R), with former President Barack Obama (L), stands with former First Lady Michelle Obama(C) as they attend the ceremony at the National 9/11 Memorial marking the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images) 
People pray at the National 9/11 Memorial and Museum during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Craig Ruttle / POOL / AFP) (Photo by CRAIG RUTTLE/POOL/AFP via Getty Images) 
Retired Paramedic Chief Charlie Wells kisses the name of a relative killed in the attack on the World Trade Center at the National 9/11 Memorial and Museum during the ceremony commemorating the 20th anniversary of the 9/11 attacks in New York, on September 11, 2021. (Photo by David Handschuh / POOL / AFP) (Photo by DAVID HANDSCHUH/POOL/AFP via Getty Images) 
Julie Sweeney Roth, whose husband Brian Sweeney Roth died when United Airlines flight 175 hit the World Trade Center, attends the National 9/11 Memorial during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Craig Ruttle / POOL / AFP) (Photo by CRAIG RUTTLE/POOL/AFP via Getty Images) 
Julia Melendez, holds a photo of her husband Antonio, who died working at Windows on the World Restaurant, at the National 9/11 Memorial during the ceremony commemorating the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Craig Ruttle / POOL / AFP) (Photo by CRAIG RUTTLE/POOL/AFP via Getty Images) 
Family members grieve at the National 9/11 Memorial and Museum after the ceremony marking the 20th anniversary of the 9/11 attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Ed JONES / AFP) (Photo by ED JONES/AFP via Getty Images) 
A woman whose father died on 9/11, lays flowers at the National 9/11 Memorial and Museum during the commemoration of the 20th anniversary attacks on the World Trade Center, in New York, on September 11, 2021. (Photo by Ed JONES / AFP) (Photo by ED JONES/AFP via Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Priscella Davis, daughter of fallen Port Authority Police Officer Clinton Davis Sr., holds her son Jaxson, 4, as they view his name during the annual 9/11 Commemoration Ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony, six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Michael M. Santiago/Getty Images) 
NEW YORK, NEW YORK – SEPTEMBER 11: Family, friends and colleagues of those killed in the 9/11 and the 1993 bombing terror attacks participate in the annual commemoration ceremony at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images)
Three presidents and their wives stood somberly side by side at the National September 11 Memorial, sharing a moment of silence to mark the anniversary of the nation’s worst terror attack with a display of unity.
Presidents Joe Biden, Dr. Jill Biden, Barack Obama, Michelle Obama, Bill Clinton and Hillary Clinton all gathered at the site where the World Trade Center towers fell two decades ago.
They each wore blue ribbons and held their hands over their hearts as a procession marched a flag through the memorial, watched by hundreds of Americans gathered for the remembrance, some carrying photos of loved ones lost in the attacks.
Mayor Bill de Blasio, as well as former mayors Michael Bloomberg and Rudy Giuliani, who was mayor on Sept. 11, 2001, all also attended the moving ceremony.
Watch the full ceremony below:
