Well, in the modern era then. I trace it to Munich in 1972, but other go further back.
Here's the chronology as I see it. I'm sure there are some that I'm missing.
1972 Munich
1979 Iran takes hostages
1983 Beirut Marine Corps Barracks bombing. (Reagan was wrong on this)
1985 TWA flight hijacked, USN Diver killed
1985 Archille Lauro hijacked, Leo Klinghoffer killed and dumped over board
1988 Pan AM 747 bombing over Lockabee, Scotland
1993 WTC first attack
1996 Bombing of Khobar Towers Military Complex
1998 US Embassies in Africa bombed
2000 USS Cole attacked
2001 WTC second attack
Arguably, attacks by regular or irregular forces against US Military personnel and stations are not terrorist attacks. That being the case, they are acts of war and the sponsoring nations should be held accountable.
Attacks by irregular forces aka terrorists against civilians violate several provisions of the Geneva Accords and as such the perpetrator when caught should be subject to military, not civilian trial and punishment. The problem with the Clinton administration's approach was to treat these a crimes, to be investigated by the FBI and prosecuted in US Courts. This was as foolish as it would have been had FDR ordered the FBI to arrest Hirohito after Pearl Harbor was attacked.
The thing that people just can't get their head around is that this is war waged by non state actors. That is, these people owe allegiance to a theology, not a nation. None the less, they are waging war. The only response is essentially what the Bush administration has done. Find and kill the terrorist where ever and when ever you can. Additionally, state sponsors, Afghanistan, Iraq, Iran, Syria, etc. have to be punished as well. Without willing host nations, the non state actors can not survive.
A friend of mine, who is rather liberal was railing on about the "domestic spying" (it isn't) that the Bush Administration is engaging in. He said that our Constitutional freedoms are more at risk from the Bush Administration than from a few, and I quote, "towel-heads with box knives". Despite being a very bright guy, he has totally misread the situation. What those people did with the box knives and what the plan to do in the future is the issue. It won't stop with giving back Gaza, the West Bank, or even Spain. What these people want, and are willing to kill and die for, is a planet with only one religion, which is both religion and government. Further, they want their particular version and are willing kill other members of their own religion to do it.