Politicians, dignitaries and victims' relatives were gathering in New York, Washington and Pennsylvania on Thursday to commemorate the nearly 3,000 people killed in al-Qaida's attack on the United States 13 years ago on September 11.
In what has become an annual ritual, relatives began slowly reciting the names of the victims at a ceremony in lower Manhattan, from Gordon Aamoth, Jr., to Igor Zukelman.
Readers would occasionally pause as a silver bell was rung to herald moments of silence marking the times when each of the four planes hijacked by Islamist militants crashed and the World Trade Center's twin towers fell.
In New York, the voice of Tom Monahan, a man with salt-and-pepper hair and broad shoulders, cracked when he talked about the brother and cousin he lost in the attack.
"Everything is fine until you get here," he said before waving his hands as if to signal he could not talk anymore.
Many people held up posters with smiling photographs of their dead relatives. Red roses and American flags poked up from the bronze plates bearing victims' names that ring the two waterfalls that now trace the footprints of the fallen towers.
In Washington President Obama, accompanied by first lady Michelle Obama and Vice President Joe Biden, led a moment of silence on the South Lawn of the White House at the time the first hijacked passenger jet crashed into one of the twin towers of New York City's World Trade Center.
Obama later spoke at the Pentagon during a private ceremony for relatives of the 184 people killed in the attack on the headquarters of the U.S. Defense Department outside Washington in Arlington, Virginia.
He laid a wreath of white lilies and mums, and kept his hand on his heart as "Taps" played.
"Thirteen years after small, hateful minds conspired to break us, America stands tall and America stands proud," Obama said, telling the victims' relatives their love was "the ultimate rebuke to the hatred of those who attacked us that bright, blue morning."
National September 11 memorial
In New York City, it is the first commemoration ceremony since the opening of the museum at the National September 11 Memorial, along with the adjoining repository for unidentified victims' remains.
The area, a smoldering grave and an off-limits construction site for more than a decade, is now increasingly reconnected with the surrounding streets as rebuilding at the site nears completion.
“For the first time this year, because the museum opened in May, family members will be able to visit the museum as part of the commemoration,” said Michael Frazier, a memorial spokesman.
Although the reconstruction has been plagued by delays, two of the new skyscrapers built around the site of the fallen twin towers are now open, while 1 World Trade Center, the tallest skyscraper in the Western hemisphere, is due to open later this year.
The only ceremony open to the general public Thursday is at the Flight 93 National Memorial in Shanksville, Pennsylvania, which marks the field where one of the four hijacked airliners crashed.
The commission that investigated the September 11 attacks concluded Flight 93 crashed as passengers fought with the hijackers to regain control of the plane. The crash site has been turned into a national memorial in honor of the plane's passengers and crew.
The Congressional Gold Medal honoring the flight's passengers and crew will go on public display for the first time, the National Park Service said.
While lower Manhattan may look and feel different this year, the external threat to the United States represented by the Sept. 11 attacks still weighs.
The United States and its allies see Islamic State, a group that began as an offshoot of al-Qaida, as an increasing danger. On Wednesday, Obama outlined plans to attack the group, which has seized large parts of Iraq and Syria and released videos of beheadings of two American hostages.
U.S. Secretary of State John Kerry said in a message sent to State Department employees on what he called “a tough day on the calendar” that no one would forget where they were 13 years ago when the U.S. was attacked and thousands were killed.
Kerry also remembered two years ago when the U.S. was attacked in Benghazi and four members of the Department of State were killed; Ambassador Chris Stevens, Sean Smith, Glen Doherty, and Tyrone Woods.