Twenty-five years have passed since the morning of September 11, 2001, when terrorist attacks forever changed America and the lives of millions around the world.

Nearly 3,000 people were killed when hijacked airplanes struck the World Trade Center in New York City and the Pentagon outside Washington, D.C. A fourth plane, United Flight 93, crashed near Shanksville, Pennsylvania, after passengers and crew members fought back against the hijackers.

On September 11, Americans once again paused to remember those who went to work, boarded airplanes or began an ordinary day but never returned home.

We remember the firefighters, police officers, emergency medical personnel and ordinary citizens who ran toward danger to help others. Their courage and sacrifice remain among the defining memories of that tragic day.

The passage of 25 years also means an entire generation of Americans has grown up with no personal memory of September 11. For them, 9/11 is history rather than a lived experience. That makes preserving the stories of those who were lost, those who survived and those who responded even more important.

Across the nation, commemorations mark the anniversary with the reading of victims’ names, the ringing of bells and moments of silence corresponding with the attacks. At the National September 11 Memorial in New York, families gather to remember loved ones whose names are inscribed at the site where the Twin Towers once stood.

September 11 remains a day of profound loss. It also reminds us of extraordinary courage, sacrifice and the unity Americans demonstrated in the aftermath of the attacks.

Twenty-five years later, we honor those who died, remember those whose lives were forever changed and ensure that future generations understand the significance of that September morning.

We will never forget.