A brief explanation of why the towers collapsed on 9/11.

A timeline of the events on September 11, 2001.

Learn the facts and numbers behind the construction of One World Trade Center in Lower Manhattan.

Discover the confluence of events that prompted the Great Recession in America and its main culprit: the subprime mortgage housing crisis.

Volunteers from the 9/11 Tribute Center remember where they were and how they reacted on September 11th, 2001.

Volunteers from the 9/11 Tribute Center reflect on how far the city and the country have come since September 11, 2001, and share the hopes they have for the future.

Before 2000, many feared the internet would crash at midnight on New Year’s Day and disrupt the world—but how real was the panic?

Knocked down by the first blast, 78-year-old Bill Iffrig and his orange running jersey became an iconic image of the 2013 Boston Marathon bombings.

Caroline Dries reacts to footage she captured from her NYU dorm on 9/11.

This video clip provided to "History Uncut" was taken immediately after the planes struck the two World Trade Center towers. We glimpse into the harrowing images of Manhattan that are not often shown in news broadcasts: a cameraman's frantic shadow fleeing the scene of disaster, emergency vehicles rendered unrecognizable by debris, and members of the NYPD who attempt to make sense out of the destruction.

Learn how decades of violence and volatility created the conditions for Al-Qaeda to rise and attack the U.S. on September 11, 2001. Understand how U.S. intelligence failed to anticipate the 9/11 attacks, despite growing threats and warning signs.

Reporter David Abel was shooting a documentary about the first woman with dwarfism to run the Boston Marathon when the bombs went off.

Evan Fairbanks reacts to footage he captured inside WTC Building 5 on 9/11.

Take a look at how 9/11 became a benchmark for whole generations of young Americans, influencing their attitudes about service, terror, and hope.

Sam Riegel and Quyen Tran react to footage they captured in Gateway Plaza on 9/11.

Volunteers from the 9/11 Tribute Center share their visions for the future after the events of September 11, 2001.

New Yorkers reflect on what the symbol of the Twin Towers meant to them and to the world.

Architects have overcome challenging terrain to build some of the world's greatest structures.

One man spends his life maintaining the elevators that will one day save the life of another.

Volunteers from the 9/11 Tribute Center reflect on the importance of sharing their stories of 9/11 with future generations.

Alice Martin, who lost her husband on September 11, 2001, gets a private tour of the memorial site and learns the story of the Survivor Tree.

A pair of wings took flight from Arkansas to Afghanistan, carrying with them the love of a mourning father.

What happened to the flag hoisted at Ground Zero on September 11, 2001?

A photographer documents the efforts of Ground Zero workers in the days after September 11th.

On 9/11, NYC ferry Captain Richard Thornton joined others in rescuing 500,000+ people by boat from Manhattan to safety.

The remarkable story of a heroic firefighter who survived the collapse of the North Tower.

John Kalymnois reacts to footage he captured in Tribeca on 9/11.

Cheryl Dunn reacts to footage she captured from her Maiden Lane apartment on 9/11.

The incredible story of Todd Beamer's call to GTE Operator and the heroism on Flight 93.

How has the United States changed in the fifteen years since September 11, 2001? How will it continue to grow?

The roots of modern day Al Qaeda can be traced back to the Muslim Brotherhood organization that began in Egypt. Find out how Osama Bin Laden made connections to the different leaders who helped him eventually plan and carry out the events of September 11th.

President George W. Bush, Donald Rumsfeld and others look back on the attack on the Pentagon on September 11, 2001.

Video footage captured on September 11th, 2001, reveals the moment tragedy struck and the moments following.

Personal tragedy brought Carlos Arredondo, "the man in the cowboy hat," to the finish line that day, but his spontaneous act of heroism helped save a life and change the course of the investigation into the attack.

Passed after the 9/11 terrorist attacks, the Patriot Act has created new rules on surveillance and national security in the U.S. See why some believe it has kept the country safer, while others believe it violates Americans' constitutional rights.

In 2015, a pediatrician discovers that Flint Michigan's water supply changed sources and ran the risk of being tainted by lead. Against public criticism, she fought to expose the problem to the wider public.

Alfie Alvarez reacts to footage she captured at City Hally Park on 9/11.

Notable New Yorkers including former mayors Rudy Giuliani and Michael Bloomberg and newsman Dan Rather remember where they were on September 11th.

Bruce Powers, a volunteer at the 9/11 Tribute Center and Pentagon employee for over sixteen years, reflects on the events of attack on the Pentagon.

After completing the 26.2 mile race, trauma surgeon Dr. David King found the energy to operate on victims of the 2013 Boston Marathon bombings.

With many states currently selling medical marijuana in store fronts, it might seem like we are ushering in a new era for cannabis as medication—but in fact, history is actually repeating itself.

Out of the rubble of the World Trade Center rose a symbol of hope for many in the days after 9/11.

Fifteen years later, volunteers from the 9/11 Tribute Center describe how the events of September 11, 2001 changed their lives.

David Vogler reacts to footage he captured from the West side on 9/11

Zac Baker learns about America’s Vet Dogs and their mission to support veterans returning to civilian life.

The remarkable story of Stanley Praimnath and Brian Clark's escape from the South Tower on 9/11.

In the aftermath of the September 11, 2001, attacks, a callery pear tree emerged from the rubble.

After September 11, 2001, a heightened sense of security became the new normal.

Mayor Rudy Giuliani and former police commissioner Bernard Kerik reflect on the measures taken to lead New York City during the September 11th attacks.

Learn about the origins of ISIS and its leader Abu Musab al-Zarqawi, who terrorized Iraq's Shia Muslims with suicide bombers. Discover how successor Abu Bakr al-Baghdadi used social media to spread international terrorism before the group weakened.

Shirley Dreifus, owner of the now-iconic flag raised at Ground Zero on September 11, 2001, tells the incredible story of the flag's role in the recovery, its disappearance, and the search to find it again.

Max Frankston reacts to footage he captured in SoHo on 9/11.

One of the most difficult issues to resolve in the design of the 9/11 Memorial was how to arrange the names of the victims, which are etched into the bronze parapets that ring the Memorial Pools.