To mark the 25th anniversary of the September 11, 2001 attacks, Americans gathered to remember the nearly 3,000 people killed when hijacked planes struck the World Trade Center, the Pentagon and a field in Pennsylvania.

The most prominent event on Friday was arguably at Ground Zero, the site in New York City where the landmark World Trade Center, known as the Twin Towers, once stood.

The buildings collapsed after two commercial jets crashed into them as part of the hijacking. A memorial and museum now sit at the site. During Friday’s ceremony, relatives of victims read the names of those killed as they have every year since the attack, surrounded by the two reflecting pools that mark the towers’ footprints.

In Arlington, Virginia, mourners also gathered at the Pentagon, where American Airlines Flight 77 crashed into the building, killing 184. United States President Donald Trump and Secretary of Defence Pete Hegseth were among those delivering remarks.

“In those harrowing days after the attacks, we saw the authentic spirit of our nation. We were all New Yorkers that day, every one of us,” Trump said at the Pentagon ceremony. “The 25 years since have shown us the even greater power of the American spirit to endure and prevail and to win.”

Families also came together in Shanksville, Pennsylvania, for an observance in honour of the passengers and crew killed aboard United Airlines Flight 93.

While it is believed the attackers aimed to crash the plane in Washington, DC, they faced a revolt from those trapped on the aircraft with them. The plane ultimately made a nosedive into a rural field, instead of hitting the attackers’ target. Forty victims were killed.

Pennsylvania Governor Josh Shapiro ordered flags in the state to fly at half-staff, to “honor the bravery of the men and women who stood up to evil and ran towards danger while others were running away”.

The attacks on September 11 marked a new era for the United States, ushering in the “global war on terror”, a decades-long effort that involved US-led wars in Iraq and Afghanistan.

There have also been lifelong consequences for survivors of the attack. Earlier this week, New York City Mayor Zohran Mamdani released government documents indicating that city officials knew about the risks of toxic exposure after the fall of the Twin Towers.

An estimated 400,000 people were exposed to chemicals including carcinogens, according to the US Centers for Disease Control and Prevention (CDC). Thousands are believed to have died from conditions like cancer in the quarter century since the attacks.