The hushed ceremony, on a sunny, breezy day, was a somber coda to a triumphal week that began with Mr. Obama’s announcement Sunday night that American commandos had killed Bin Laden in his fortified compound in Pakistan.
Unlike so many other memorials held in this place, Thursday’s was not just to mourn those who died but to celebrate that, at last, a measure of justice had been done.
In a four-hour visit that included stops across Manhattan, the president held one-to-one meetings with people whose lives had been wrenched apart by Bin Laden: relatives of the victims, as well as firefighters, police officers, and other rescue workers who lost comrades that morning nearly a decade ago.
“Obviously, you can’t bring back your friends that were lost,” Mr. Obama said to the crew at a firehouse in Midtown that lost 15 men, an entire shift, at the World Trade Center.
“What happened Sunday, because of the courage of our military and the outstanding work of our intelligence, sent a message,” he declared. “When we say we will never forget, we mean what we say.”
The visit was Mr. Obama’s first as president to the patch of lower Manhattan that the attacks turned into hallowed ground. And the president was clearly eager throughout the day to remind the American public of the deeply personal reasons he ordered a risky, violent military operation half a world away.
“A lot of you have probably comforted loved ones of those who were lost; a lot of you have probably looked after kids who grew up without a parent,” Mr. Obama said to police officers at the First Precinct station house. “What we did on Sunday was directly connected to what you do every single day.”
Administration officials played down Mr. Obama’s absence from ground zero since he entered the White House. He visited in 2008 as a presidential candidate and plans to return this September for the 10th anniversary of the attacks, they said.
In 2009 and 2010, he went to the memorial for those killed at the Pentagon.
Nobody at ground zero seemed to begrudge the president his decision to visit now, even the construction workers who had been expelled from the site so security teams could sweep it before his appearance.
“Bin Laden’s death, that’s a long time coming,” said one of the workers, Eric Bellaby, 31, of Rockland County. “It’s something we all wanted for a long time. So it’s a feeling of relief now that he’s gone.”
Two hours before Mr. Obama’s arrival, hundreds of onlookers had already gathered south of the site, at the intersection of Greenwich and Liberty Streets. As the crowds waited to pass through tight security, a woman peddled $2 American flags and buttons that said “Mission Accomplished.”
Mr. Obama placed the wreath at the foot of a tree, known as the Survivor Tree, that had been wrested from the rubble, nursed back to health, and replanted as a memorial.
Then he stood silently, his head bowed and his hands clasped before him. Behind him loomed one of the cranes that are rebuilding the site, briefly stilled.
Uniformed rescue workers stood in an honor guard, alongside relatives of the victims.
Mr. Obama sought out a 14-year-old girl at the memorial, Payton Wall, who had recently written him a letter about the loss of her father, Glen James Wall, in the attack. He also met privately with 60 other relatives of the victims.
“It means, like, the world to me,” Christopher Cannizzaro said of meeting the president after the ceremony. The boy, who was 10 months old when his father, Brian Cannizzaro, a firefighter from Brooklyn, was killed, gave Mr. Obama a fist-bump and a prayer card with his father’s picture.
His mother, Jackie Cannizzaro-Harkins, said, “It gave us a sense of closure.”
Manny Fernandez contributed reporting.
