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There were moments of silence, volunteer projects and a new monument to victims, after a year when two attacks demonstrated the enduring threat of terrorism in the nation's biggest city.
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The events of that terrible day and the weeks, months and years that followed are never forgotten, nor are the memories of those killed by terrorists at the Wold Trade Center, the Pentagon, and a field in Pennsylvania. Additionally, we remember all those who have died from 9/11-related illnesses from their heroic work at ground zero and those who suffer today.
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Family and friends of the victims, survivors, rescuers and others once again gathered on at the memorial plaza where the World Trade Center's twin towers once stood, this time on a misty Tuesday morning.
Margie Miller was among them, having traveled from her home in Baldwin as she does 10 or so times a year to remember her husband, Joel Miller. Only a few fragments of his remains were recovered.
"To me, he is here," she said. "This is my holy place."
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The ceremony began with a moment of silence and tolling bells at 8:46 a.m., the time when the trade center was hit by the first of two terrorist-piloted planes.
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Nearly 3,000 people died in the attacks on 9/11, when international terrorism hit home in a way it previously hadn't for many Americans. September 11 still shapes American policy, politics and everyday experiences in places from airports to office buildings, even if it's less of a constant presence in the public consciousness after 17 years.
A stark reminder came not long after last year's anniversary: A truck mowed down people, killing eight, on a bike path within a few blocks of the World Trade Center on Halloween. Then in December, a would-be suicide bomber set off a pipe bomb in a subway passageway near Times Square, authorities said. They said suspects in both attacks were inspired by the Islamic State extremist group.
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The 9/11 commemorations are by now familiar rituals, centered on reading the names of the dead. But each year at ground zero, victims' relatives infuse the ceremony with personal messages of remembrance, inspiration and concern.
Hours after the ceremony, two powerful light beams will soar into the night sky from lower Manhattan in the annual "Tribute in Light."
President Donald Trump and Vice President Mike Pence headed to the two other places where hijacked planes crashed on September 11, 2001, in the deadliest terror attack on American soil.
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The president and first lady Melania Trump joined an observance at the September 11 memorial in a field near Shanksville, Pennsylvania, where a new "Tower of Voices" was dedicated Saturday. Pence is attending a ceremony at the Pentagon.
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Memorials to 9/11 continue to grow at Shanksville, where the Tower of Voices will eventually include a wind chime for each of the 40 people killed there, and ground zero, where work is to begin soon on a pathway honoring rescue and recovery workers.
It will serve as a way to honor those who became sick or died from exposure to toxins released when the Trade Center's twin towers collapsed. Researchers have documented elevated rates of respiratory ailments, post-traumatic stress disorder and other illnesses among people who spent time in the rubble.
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About 38,500 people have applied to a compensation fund, and over $3.9 billion in claims have been approved.
Meanwhile, rebuilding continues. A subway station destroyed on 9/11 finally reopened Saturday. In June, doors opened at the 80-story 3 World Trade Center, one of several rebuilt office towers that have been constructed or planned at the site. A performing arts center is rising. And a new exhibit at the National September 11 Memorial and Museum shows the dramatic impact sports had on the nation's recovery.
See more stories, photos, and video on 9/11 ceremonies.
The Associated Press contributed to this report