A steel beam from the South Tower of the World Trade Center made a stop at the Ellipse in Washington on Tuesday, where President Donald Trump honored the 2,977 individuals who died during the Sept. 11, 2001, terrorist attack on the United States.

“We gather on another Tuesday morning in September to reaffirm the sacred vow we made a quarter of a century ago: We will never forget,” Trump said at a 25th anniversary event where he was joined by first responders, members of the military and Trump administration officials. “We say it, and we mean it.”

Like many Americans, Trump recalled exactly where he was when terrorists hijacked four passenger airplanes, crashing one of them into the Pentagon in Washington and two into the World Trade Center towers in New York, while another plane crashed into a field in Shanksville, Pennsylvania.

“Sept. 11 was one of those moments in time where everybody knows exactly where they were,” said Trump, who recalled being in New York on a beautiful morning when he looked out of his window “and saw things that I never want to see again. … In just over 100 minutes, 175,000 tons of steel and concrete were reduced to ruin, and 3,000 lives were extinguished immediately.”

One of those pieces of steel — a 21-foot-long, 16,000-pound beam recovered from the World Trade Center — has been touring the country since May, traveling over 10,500 miles across 21 states and Washington, D.C., as part of the Steel Across America commemoration.

Organized by the nonprofit Tunnel to Towers Foundation, which was created to memorialize New York firefighter Stephen Siller, who died on 9/11, and to honor the sacrifices of first responders, military members and their families, Steel Across America’s stop in Washington was part of a 40-city tour that will conclude Friday in New York City as part of a ceremonial procession through the Brooklyn-Battery Tunnel.

“This steel beam represents the best of our country,” Tunnel to Towers Foundation Chairman Frank Siller said at Tuesday’s event. “It is how we honor the sacrifice that was made.”

Those sacrifices include Frank Siller’s firefighter brother, 40 passengers and flight crew who died in the Pennsylvania crash, 184 who died from the Pentagon attack and 2,753 who died in the World Trade Center on 9/11. Six hundred fifty-eight of those killed at the World Trade Center worked at the Cantor Fitzgerald investment firm that was located on the center’s top three floors and was led at the time by now-Commerce Secretary Howard Lutnick.

Trump said Tuesday that Lutnick was almost always at his office in the mornings, but on 9/11, at the insistence of his wife, he instead took their son to school. That son, Brandon Lutnick, is now chair of Cantor Fitzgerald.

Lutnick was one of several members of Trump’s Cabinet who were at Tuesday’s event, including Attorney General Todd Blanche, Homeland Security Secretary Markwayne Mullin, Environmental Protection Agency Administrator Lee Zeldin, Office of Management and Budget Director Russell Vought and Secretary of Veterans Affairs Doug Collins.

Rep. Mike Lawler, R-N.Y., was also in attendance, having been the primary advocate for a Presidential Medal of Honor that Trump bestowed upon the family of Welles Crowther at Tuesday’s event.

A 24-year-old equity trader and volunteer firefighter from Rockland County in New York, Crowther is remembered as the “man in the red bandanna” for saving as many as 18 lives in the World Trade Center’s South Tower, where he worked, before dying when the building collapsed.

Trump said the medal is to honor “his incredible bravery and all of the other countless unknown acts of heroism that day.”

According to the Fire Department of New York, 343 of its members died responding to the attacks at the World Trade Center on 9/11. It was the largest loss of emergency responders in U.S. history.

Following the worst-ever terrorist attack on U.S. soil, more than 400 additional FDNY firefighters died because of toxic exposures at the World Trade Center site that caused cancer and respiratory diseases, the agency said.