September 11, 2001, began as an ordinary Tuesday morning. Within less than two hours, the United States—and much of the world—had changed forever. 
On September 11, 2026, Americans mark 25 years since the terrorist attacks of 9/11, remembering the nearly 3,000 people who were killed, the first responders who ran toward danger, the families whose lives were forever changed, and the generations of Americans who served their country in the years that followed.
For many Americans, the images of that morning remain as vivid today as they were 25 years ago.
For younger generations, however, September 11 is something they know only through photographs, videos, classrooms and the stories of those who lived through it.
That makes remembering what happened—and understanding how it changed America—more important than ever.
What Happened on September 11, 2001?
On the morning of September 11, 19 terrorists associated with al-Qaeda hijacked four commercial passenger aircraft departing from airports on the East Coast.
At 8:46 a.m. Eastern Time, American Airlines Flight 11 struck the North Tower of the World Trade Center in New York City.
At first, many watching the news believed the crash might have been a terrible accident.
Seventeen minutes later, at 9:03 a.m., United Airlines Flight 175 struck the South Tower.
America now knew it was under attack.
At 9:37 a.m., American Airlines Flight 77 crashed into the Pentagon in Arlington, Virginia, the headquarters of the U.S. Department of Defense.
At 9:59 a.m., the South Tower of the World Trade Center collapsed.
Then came the story of United Airlines Flight 93.
Passengers and crew members aboard the fourth hijacked aircraft learned through telephone calls that other aircraft had already struck the World Trade Center and Pentagon. They fought back against the hijackers.
At 10:03 a.m., Flight 93 crashed into a field near Shanksville, Pennsylvania. Investigators concluded that the aircraft had been heading toward Washington, D.C.
At 10:28 a.m., the North Tower collapsed.
In just 102 minutes from the impact of the first plane to the collapse of the North Tower, the American landscape and the nation’s sense of security had been permanently altered. (911 Memorial)
Nearly 3,000 Lives Lost
The September 11 attacks killed 2,977 victims from more than 90 countries.
According to the National September 11 Memorial & Museum, 2,753 people were killed in New York, 184 were killed at the Pentagon and 40 passengers and crew members were killed aboard Flight 93.
Among the dead were office workers, airline passengers and crews, military personnel, visitors and hundreds of first responders.
The attack resulted in the largest loss of rescue personnel in American history. 343 New York City firefighters, 37 Port Authority police officers and 23 New York Police Department officers were among those killed. (911 Memorial)
Yet alongside the horror were extraordinary acts of courage.
Firefighters climbed stairwells as thousands of people were coming down. Police officers, paramedics and civilians helped strangers escape. Passengers aboard Flight 93 fought back knowing what had happened to the other planes.
Thousands of people survived because others chose to help.
America Changed After 9/11
September 11 was not only a devastating attack. It became a dividing line in modern American history.
There was America before 9/11—and America after it.
Many security procedures, government agencies and counterterrorism programs that Americans now consider routine were created or dramatically expanded because of what happened that morning.
Airport Security Was Transformed
Anyone who flew commercially before September 11, 2001, remembers that airports were very different.
Following the attacks, Congress passed the Aviation and Transportation Security Act, and the Transportation Security Administration, or TSA, was formally created on November 19, 2001. (Transportation Security Administration)
Passenger and baggage screening became a federal responsibility at U.S. airports. Security checkpoints became much more extensive, and aviation security increasingly incorporated new technologies and procedures designed to prevent weapons and explosives from reaching aircraft.
For millions of Americans, airport security remains one of the most visible everyday legacies of September 11.
The Department of Homeland Security Was Created
The attacks also exposed problems in how different government agencies communicated and coordinated information.
Congress passed the Homeland Security Act of 2002, creating the Department of Homeland Security.
The new Cabinet-level department brought 22 agencies and offices together under a broader homeland-security mission. DHS began operations in 2003. (DHS)
Its responsibilities now touch numerous areas of American life, including border security, cybersecurity, disaster response, transportation security and protection of critical infrastructure.
U.S. Intelligence Was Restructured
Another major lesson of September 11 involved intelligence sharing.
Investigations into the attacks examined information that had been held by different government agencies and whether pieces of intelligence might have been better connected before the attacks.
The bipartisan 9/11 Commission recommended sweeping changes to the U.S. intelligence system. Congress subsequently passed the Intelligence Reform and Terrorism Prevention Act of 2004.
Those reforms contributed to the creation of the Director of National Intelligence and National Counterterrorism Center, with greater emphasis placed on coordinating and sharing terrorism-related intelligence across government agencies. (ODNI)
The idea was straightforward: agencies charged with protecting the country needed to communicate better.
September 11 Changed U.S. Foreign Policy
The attacks also launched the United States into a new era of warfare and counterterrorism.
On October 7, 2001, less than a month after September 11, the United States began military operations in Afghanistan against al-Qaeda and the Taliban government that had provided the terrorist organization with safe haven. (U.S. Department of War)
What followed became America’s longest war.
For the next two decades, Americans served overseas in military, intelligence, diplomatic and support roles as the United States pursued terrorist organizations and attempted to prevent another large-scale attack on American soil.
Thousands of American service members died during the Afghanistan war, while many more returned home carrying physical and psychological wounds.
Families across Texas and throughout the United States experienced deployments, missed birthdays, holidays away from home and, for some, the devastating loss of a loved one.
The consequences of September 11 therefore extended far beyond New York, Virginia and Pennsylvania.
They reached communities across the country—including Katy and the Greater Houston area.
The Health Effects Continue 25 Years Later
The death toll of September 11 cannot be understood only by counting those who died that morning.
When the World Trade Center collapsed, enormous clouds of dust, smoke and debris spread throughout Lower Manhattan.
Firefighters, police officers, construction workers, volunteers, residents, students and others were exposed to hazardous conditions during the attacks and the months of rescue, recovery and cleanup that followed.
The CDC’s World Trade Center Health Program says decades later, thousands of people continue to experience physical and mental health conditions associated with their 9/11 exposure, including respiratory illnesses, cancers and post-traumatic stress disorders. (CDC)
As of 2026, the federal program serves nearly 150,000 responders and survivors across the United States. (CDC)
For them, September 11 did not end when the smoke cleared.
Security, Freedom and a National Debate
The years after 9/11 also changed how Americans thought about privacy, surveillance, immigration, national security and civil liberties.
The challenge of stopping terrorism while protecting constitutional freedoms became one of the defining public-policy debates of the post-9/11 era.
Americans became accustomed to security measures that would have seemed unusual before September 2001—from enhanced airport screening to increased security around government buildings, large public events and critical infrastructure.
Local police, firefighters and emergency-management agencies also increasingly trained for large-scale attacks and coordinated responses with state and federal agencies.
The country’s definition of “homeland security” had fundamentally changed.
A Moment of National Unity
There was another change following September 11 that Americans who lived through the period still remember.
For a time, many of the political, cultural and regional divisions of everyday life seemed secondary.
American flags appeared on homes, businesses, vehicles and highway overpasses.
People donated blood, volunteered, raised money for victims’ families and looked for ways to help.
Firefighters, police officers, military personnel and other first responders received an extraordinary level of public recognition.
Americans also heard countless stories of ordinary people helping strangers.
That sense of unity remains an important part of the memory of September 11.
Twenty-Five Years Later, Why Remembering Still Matters
September 11 is gradually moving from living memory into American history.
A person born after September 11, 2001, can now be an adult with a career and a family of their own.
They never experienced an airport before modern TSA security. They did not see the Twin Towers standing over Manhattan. They did not watch classrooms and workplaces suddenly stop as television screens showed the attacks unfolding.
For them, September 11 must be taught.
But teaching 9/11 should involve more than showing images of burning buildings.
It should include the names and lives of the people who were lost.
It should include the firefighters who climbed the towers.
It should include the police officers, paramedics and civilians who helped strangers.
It should include the passengers of Flight 93 who fought back.
It should include the military families whose lives were shaped by the wars that followed.
And it should include the responders and survivors who continue facing health consequences decades later.
Never Forget
Every September 11, the names of the victims are read aloud at the National September 11 Memorial in New York.
Moments of silence mark the times the planes struck the World Trade Center and Pentagon, the time Flight 93 crashed and the moments when the Twin Towers fell.
Twenty-five years later, America’s skyline has changed.
Its airports have changed.
Its military has changed.
Its intelligence agencies have changed.
Its emergency-response systems have changed.
And an entire generation has grown up in the world that September 11 created.
But the most important part of remembering September 11 remains unchanged.
Remember the people.
Remember those who went to work that morning and never returned home.
Remember those who boarded four airplanes expecting an ordinary flight.
Remember the first responders who ran toward danger while others were running away.
Remember the families who continue to carry their loss.
And remember the courage, sacrifice and unity Americans showed when the country faced one of its darkest days.
Twenty-five years later, we remember September 11, 2001.
We remember the lives lost. We honor those who served. And we make certain that future generations understand why America promised: Never Forget.
