“Unity,” he added, “is what makes us who we are, America at its best. To me, that’s the central lesson of Sept. 11.”
In New York, the president and first lady, Jill Biden, stood shoulder to shoulder at the 9/11 memorial plaza with two pairs of their Democratic predecessors, Barack and Michelle Obama and Bill and Hillary Clinton, who was a senator of New York 20 years ago. Nearby was Rudolph W. Giuliani, a Republican who was the mayor of New York during the attacks and has since become one of Mr. Biden, Mrs. Clinton and Mr. Obama’s most vociferous critics.
All of them watched as families of the victims read the names of the dead, tears streaming down their cheeks and their voices shaking. The recitation paused for moments of silence marking the times when the hijacked planes hit their targets and when the twin towers eventually fell. As the plaza fell silent, church bells rang.
Bruce Springsteen, the songwriter and singer so closely linked to the New York region, took a moment to honor the victims, performing “I’ll See You in my Dreams,” a song about death and loss.
Many of those who read names at the memorial were children, either born after the attacks or too young to remember the friends and family members who died. Ms. Reina, whose husband worked at Cantor Fitzgerald, the bond trading firm that lost 658 employees in the attack, was pregnant on 9/11. Her son is part of an entire generation that has been born in the shadow of that day and has only received its legacy secondhand.
Ariana and Briana Mendoza, 13, came to Lower Manhattan from the Bronx with their sister Dephaney to pay their respects. “I was only 2 when it happened,” Dephaney, 22, said. “But I have learned a lot about it, and now I am teaching them.”
Nearby, Luis Gonzalez, 41, of Staten Island, stood staring up at One World Trade Center, the tower built upon the ruins of ground zero that shoots above Manhattan like a gleaming beacon of Lower Manhattan’s recovery and resilience. He carried a poster of the old twin towers that now hangs in his bedroom. “I come out of respect,” he said.