The U.S. marked the 15th anniversary of 9/11 on Sunday, with victims' relatives reading their names and reflecting on a loss that still felt as immediate to them as it was indelible for the nation.
Hundreds of victims' family members, survivors and dignitaries gathered at ground zero under an overcast sky that shrouded the 1,776-foot-tall top of One World Trade Center, the centerpiece of the rebuilt site.
"It doesn't get easier. The grief never goes away. You don't move forward - it always stays with you," said Tom Acquaviva, of Wayne, New Jersey, who lost his son Paul Acquaviva.
James Johnson, a retired New York City police sergeant who is now police chief in Forest City, Pennsylvania, came to ground zero for the first time since he last worked on the rescue and recovery efforts in early 2002.
"I've got mixed emotions, but I'm still kind of numb," he said. "I think everyone needs closure, and this is my time to have closure."
Nearly 3,000 people died when hijacked planes slammed into the World Trade Center, the Pentagon and a field near Shanksville on Sept. 11, 2001. It was the deadliest terror attack on American soil.
President Barack Obama says the nation will never forget the lives of those killed in the attacks. Obama said at a Pentagon memorial service that he is inspired by the resilience of the victims' families.
He quoted Scripture: "Let not steadfast love and faithfulness forsake you. Bind them around your neck. Write them on the table of your heart."
Obama also praised America's diversity and urged Americans not to let their enemies divide them. He called the day "difficult" but one that "reveals the love and faithfulness in your hearts and in the heart of our nation."
The 15th anniversary arrives in a country caught up in a combustible political campaign, and keenly focused on political, economic and social fissures.
But some at the ceremony pleaded for the nation to look past its differences.
"The things we think separate us really don't. We're all part of this one Earth in this vast universe," said Granvilette Kestenbaum, who lost her astrophysicist husband, Howard Kestenbaum. "We're all ordinary, and we're all special, we're all connected. We waste precious time by thinking otherwise."
The nation tries to put partisan politics on hold on the anniversary, and both Democratic presidential candidate Hillary Clinton and Republican rival Donald Trump were at the anniversary ceremony at the World Trade Center. Neither candidate was expected to make public remarks at a ceremony where politicians have been allowed to attend, but not speak, since 2011.
Clinton and Trump also followed a custom of halting television ads for the day.
While ground zero and the nation around it are forever marked but greatly changed since 9/11, the anniversary ceremony itself has become one of the constants in how America remembers the attacks after 15 years.
Organizers included some additional music and readings Sunday to mark the milestone year. But they were keeping close to what are now traditions: moments of silence and tolling bells, an apolitical atmosphere and the hourslong reading of the names of the dead.
"This idea of physical transformation is so real here," Sept. 11 memorial President Joe Daniels said this week. But on this Sept. 11 itself, "bringing the focus back to why we did all this - which is to honor those that were lost - is something very intentional."
The simple, reverential observance may be the norm now, but city officials fielded about 4,500 suggestions - including a Broadway parade honoring rescue workers and a one-minute blackout of all of Manhattan - while planning the first ceremony in 2002.
Financial and other hurdles delayed the redevelopment of the Trade Center site early on, but now the 9/11 museum, three of four currently planned skyscrapers, an architecturally adventuresome transportation hub and shopping concourse and other features stand at the site. A design for a long-stalled, $250 million performing arts center was unveiled Thursday.
Around the Trade Center, lower Manhattan now has dozens of new hotels and eateries, 60,000 more residents and ever-more visitors than before 9/11.
Meanwhile, the crowd has thinned somewhat at the anniversary ceremony in recent years. But there's been no sustained talk of curtailing the ceremony.
Cathy Cava, who lost her sister, Grace Susca Galante, has attended all 15 years.
"I will keep coming as long as I am walking and breathing," Cava said, wearing a T-shirt with her sister's photo.
"I believe most of her spirit, or at least some of her spirit, is here. I have to think that way."