Victims' family members were on hand at the memorial service to pay tribute to their loved ones, and many participated in reading the names of those lost on that day. Also there to pay tribute were New York Gov. George Pataki and former New York City Mayor Rudolph Giuliani.
"We've come back to remember the valor of those we've lost, those who innocently went to work that day and the brave souls who went in after them," said Giuliani.
At Ground Zero, family members descended to the lowest level of the Trade Center site, gathering around two reflecting pools where the Twin Towers once stood.
Meanwhile, at a Monday ceremony at the Pentagon, where 184 people on American Flight 77 perished, Vice President Dick Cheney and Defense Secretary Donald H. Rumsfeld contributed their voices to the "Battle Hymn of the Republic" before observing a moment of silence at 9:37 a.m., the time the plane struck.
"We have no intention of ignoring or appeasing history's latest gang of fanatics trying to murder their way to power," Cheney said.
In a field in Shanksville, Pa., where 40 people crashed onboard United Flight 93 after passengers wrestled control from its hijackers, hundreds of mourners gathered in prayer at a temporary memorial comprised of a 10-foot chain-link fence blanketed with American flags, firefighter helmets and children's drawings.
Spencer Platt / REuters / Landov
On Sunday, President Bush began two days of marking the fifth anniversary of the 9/11 attacks by paying tribute to the victims of the tragedy.
He laid wreaths of red, white and blue flowers at Ground Zero, attended a prayer service at the nearby St. Paul's Chapel and visited a firehouse and its adjacent memorial museum near the site where the towers once stood.
Outside the firehouse, the president clutched his wife's hand and told reporters that this year's commemoration was about "renewing resolve," the Associated Press reports.
Of those who lost loved ones on 9/11, the president said, "You know, you see the relatives of those who still grieve – I just wish there were some way we could make them whole."
During the service at St. Paul's, Jane Vigiano, who lost her two sons – Joe, a policeman, and John, a firefighter – sat next to the president, The New York Times reports. On Laura Bush's side was Bob Beckwith, the retired firefighter who handed Bush the bullhorn he used to vow vengeance when he visited Ground Zero just days after the attacks.
In the same row sat Arlene Howard, the mother of New York Port Authority police officer of George Howard, also killed that day. The president has said he keeps Howard's badge as a constant reminder of the attacks.
In his sermon, the Rev. Timothy J. Keller of Redeemer Presbyterian Church in Manhattan said he still struggles with how to reconcile the tragedy of 9/11 with his faith in God, The Times reports.
"The very best way to honor the memories of the ones that we've lost and loved is to live productive, confident lives,'' Keller said. "We have to have the strength to face the world filled with constant devastation and loss."
FABIANO / EPA