It has been twenty years since the September 11 terrorist attack also known as 9/11, on the World Trade Center. We still remember that day and where we were.
A Normal Day
The day began normal on September 11, 2001. Workers were going to their jobs expecting a normal work day. Little did they know what was to happen.
The First Plane
At 8:46 am, the hijacked American Airlines Flight 11 slammed into the North Twin Tower of the World Trade Center.
The Second Plane
While some people might have thought this was just an accident, they soon came to realize that it was not. A second plane, United Airlines Flight 175 crashed into the South Twin Tower at 9:03 am.
After the second hijacked plane hit the South Twin Tower, people started evacuating the towers, but lots of people were stuck on the top floors. Emergency workers came from around the New York City and started helping get the people out. By 10:30 am, both towers had collapsed with people still inside. Over 2,800 people died on September 11th.
A Third Attack
The attack on the Twin Towers were not the only terrorist attack, the terrorists hijacked American Airlines Flight 77 and crashed it into the Pentagon Building in Washington, D.C., at 9:37 am. 
A Fourth Plane
The terrorists were not done yet. United Airlines Flight 93 was hijacked. The passengers and the crew of Flight 93 fought back against the hijackers and crashed the plane in Shanksville, Pennsylvania, at 10:03 am.  It was later surmised that the hijacked plane was headed for the White House or the U.S. Capitol.
President Bush’s Message
President George W. Bush gave a speech to the nation. In the message, he said,
Freedom itself was attacked this morning by a faceless coward. And freedom will be defended. 
Since no one knew if another hijacked plane would attack an important place or city, the airline traffic was stopped in the United States. All the federal buildings in Washington, D.C., key airports, and other likely terrorist targets around the country were evacuated.
The Terrorist Group
It was later found out that Islamic Osama bin Laden, the leader of terrorist group al-Qaeda, had been the cause of the attack. In 2011 Osama bin Laden was killed by the U.S. military.