Members of the New York Police Department, New York Fire Department and the Port Authority Police Department carry an American flag at the beginning of the memorial observance held at the site of the World Trade Center in New York on Thursday. (Andrew Burton/EPA)

Crowds of somber mourners gathered in New York, Washington and Pennsylvania on Thursday morning to mark the 13th anniversary of the Sept. 11, 2001 attacks.

The proceedings carried with them a stark reminder of that day’s losses, cutting through more than a decade of change and war to emphasize that the largest terrorist attack in U.S. history was more than an epochal, historic event; it was a day when nearly 3,000 people were killed after hijackers crashed four jetliners in three different locations on the East Coast, leaving behind thousands of mourners as well as a scarred national psyche.


A single rose is seen on inscribed names on the edge of the North Pool during the ceremony. (Robert Sabo/Reuters)

In New York, a commemoration at the National September 11 Memorial Museum began with a moment of silence to mark the moment the first plane struck the North Tower at 8:46 a.m. It was followed by the recitation of names of people killed that day and more than eight years earlier, when a bomb was detonated in the building’s garage.

As family members read aloud the names of people killed that day, they paused for moments of silence at the times that have become etched in memory during these annual remembrances: When the second plane struck the South Tower (9:03 a.m.), when Flight 77 crashed into the Pentagon outside of Washington (9:37 a.m.), when the South Tower fell (9:59 a.m.), when Flight 93 crashed in Pennsylvania (10:03 a.m.) and when the North Tower fell (10:28 a.m.). 


Maria Cioccone of New York places a flower in the inscribed name of her son Alex along the edge of the North Pool during the memorial ceremony. (Justin Lane/AP)

 (A livestream of the ceremony in New York is available here.) 

This ceremony in New York, which follows a pattern established and followed each year, is expected to be the last before the opening of One World Trade Center, a 1,776-foot-tall office tower that has risen above Ground Zero. While a precise opening date is unknown, the Port Authority expects it will open later this year.

More than a decade later, it remains difficult for those who lost loved ones to return to Ground Zero.

“Coming down to the area is rough,” Franklin Murray, who lost his brother in the attacks, told the Associated Press. He has come to the ceremony before, but “it was getting harder, so I forced myself to get down here,” he said.

The memorial’s “Tribute in Light” will illuminate the skies over Manhattan beginning at 6 p.m. Thursday, as another way to remember those who died, according to the 9/11 Memorial. The memorial itself, which opened in May, will remain open until midnight, offering an opportunity for those who can’t visit during the ceremony.

Outside Washington, President Obama spoke at the Pentagon, telling family members of victims who had gathered at the facility’s open-air memorial that the attacks “sought to break our spirit,” but that the perseverance showed by the families and other Americans “proved them wrong.”

Earlier on Thursday morning, he was joined by first lady Michelle Obama and Vice President Biden for a moment of silence on the south lawn of the White House.


President Obama, first lady Michelle Obama and Vice President Biden walking onto the South Lawn on Thursday. (Chip Somodevilla/Getty Images)

In Shanksville, Pa., where United Airlines Flight 93 crashed, a remembrance was held at the memorial, which sits amid wide, expansive fields of grass in southwest Pennsylvania.

The memorial in Shanksville on Thursday included the first public display of the Congressional Gold Medal awarded to the passengers and crew who died that day.

President Obama, the first lady and Vice President Joe Biden led a moment of silence at the White House in memory of the victims of the Sept. 11, 2001 attacks. (AP)