The September 11 twin attacks or simply know as 911 attacks are important in US history because it was the first time that terrorists have inflicted harm on almost 2,000 US citizens. It was also the first time in US history where a major breech in the airport security have allowed terrorists to fly planes and crash them into the World Trade Center buildings. The Americans commemorate 911 as a day when many US citizens have lost their loved ones on a tragic attack. For information as to what transpired during September 11, 2001 go to this site: http://www.ask.com/wiki/September_11_attacks
September 11, 2001 is important to American's because it was the day our country was attacked by terrorism and many innocent lives were lost. We reflect back to remember those who died helping and who died at the hands of terrorism.