The September 11 attacks struck the nation on a clear, late summer morning on the East Coast. Hijackers used jet airliners as weapons and rammed them into New York City's World Trade Center and the Pentagon. One hijacked plane crashed in a field outside Shanksville, Pennsylvania. In all, 2,977 were killed.
As New York City's Mayor Rudy Giuliani said five hours after the attacks began, “The number of casualties will be more than any of us can bear, ultimately.”
Below are images from September 11 and the aftermath.
WATCH: Commemorating the 20th anniversary of the September 11 attacks, The HISTORY® Channel will premiere three documentary specials, starting on September 10. Watch a preview for all three specials now.
Attacks on the World Trade Center: Photos
Militants associated with the Islamic extremist group al Qaeda hijacked four airplanes on 9/11. At 8:46 a.m., Flight 11 hit the north tower of the World Trade Center. At 9:03 a.m., Flight 175 crashed into the south tower. The south tower collapsed at 9:59 a.m., less than an hour after being hit, and the north tower fell at 10:28 a.m., causing massive damage to the rest of the complex and nearby buildings.
In all, 2,595 people inside and near the towers were killed, along with the 157 people who were aboard the flights.
NYC First Responders on 9/11: Photos
The 9/11 attacks not only became the single deadliest terrorist attack in human history, they were also the deadliest incident ever for firefighters, as well as for law enforcement officers in the United States.
READ MORE: How 9/11 Became the Deadliest Day in History for U.S. Firefighters
Recommended for you
Attack on the Pentagon: Photos
At 9:37 a.m. on September 11, 2001, a jet engine roared low over traffic in Washington, D.C. The airplane, the hijacked American Airlines Flight 77, sliced through three light poles in the Pentagon parking lot before slamming into the first floor of the building and exploding in a fireball, instantly killing 125 people inside the Pentagon plus all 64 passengers onboard, including the five hijackers.
READ MORE: How the Pentagon's Design Saved Lives on 9/11
READ MORE: Pentagon - Location, Building Timeline, 9/11
Flight 93: Photos
United Airlines Flight 93, a regularly scheduled early-morning nonstop flight from Newark, New Jersey, to San Francisco, California, departed at 8:42 a.m. on September 11, 2001, just minutes before the first hijacked plane struck the World Trade Center. Unlike the hijackers on the other three planes, the four hijackers on Flight 93 did not attempt to gain control of the aircraft until nearly 40 minutes into the flight. Flight 93's passengers and crew fought back.
READ MORE: Flight 93 - Hijackers, Passengers & Crash
READ MORE: How United Flight 93 Passengers Fought Back
READ MORE: On 9/11, Heather Penney Tried to Bring Down Flight 93 in a Kamikaze Mission
The President and Vice President on 9/11: Photos
On 9/11, millions of Americans became glued to their televisions, watching in horror as hijacked planes attacked the World Trade Center and the Pentagon. But there was one critical group of people who, for a time, received only snippets of information—and misinformation—as the day unfolded. They were the passengers of Air Force One—including the president of the United States, George W. Bush.
Vice President Dick Cheney, meanwhile, was rushed to a White House bunker and was in the decision-making hot seat.
9/11 Lost and Found: The Items Left Behind
A few years after the 9/11 attacks, work began at New York City's Ground Zero to build what would become the 1,776-foot-tall Freedom Tower and the National September 11 Memorial and Museum. In May of 2014, the 9/11 Memorial Museum opened in New York by the World Trade Center site. The museum honors the many victims of the attacks and all those who risked their lives to rescue and save others. Among the museum's collections are over 11,000 artifacts collected from Ground Zero, donated by survivors and victims’ loved ones.