All I knew was the attack on the towers and on the Pentagon.
Those are the most commonly known, yes. But part of the reason it's remembered is because the passengers on that plane all agreed to give their life to stop the plane from hitting the Capitol.
Really, that's why the date was remembered so well, or at least should be. Not the fact many people died - even as sad and horrid that is, don't get me wrong - but for the fact that many joined together despite their differences in order to reach a common cause and in order to help someone else; Even one who they may not know. Basically the same reason Americans honor their military. As such, the pure irony of that day is one of the biggest reasons it's remembered.
September 11, 2000 was the greatest September 11 ever lived.
September 11
th, 1894 wasn't that bad, either. :D