re: O.K., So how many were there before 9/11?
There was the first WTC attack in 1993. Some might put the OK City bombing in with this. The USS Cole was US property. The US Embassy in Africa was US property.
That is all in the past, of course. What matters is that 9/11 was the worst. Many attacks have been foiled since then ( A few, like that mall incident, we have heard about. Tons more that we are probably not hearing about.)
Anyway, none have happened on American soil since 9/11.