Patriot Day is a national day of mourning on September 11 every year in memory of the people killed by Islamic extremist group al-Qaeda in the WTC attacks on September 11, 2001.
The Twin Towers were 110-stories tall. One plane hit the North Tower, one plane hit the South Tower. A third plane hit the Pentagon. The fourth plane hit a field in Pennsylvania.
2,996 people killed (including all 246 passengers and crew aboard the four planes)