Not just one, but several "firsts" in the history of architecture on 9/11....
1. First time a steel framed building ever collapsed due to fire.... Never before or since 9/11 has any steel framed build ever collapsed due to fire.
2. First time a non-engineered gravitational collapse ever completely pulverized all the contents of a building to dust.... Desks, chairs, carpet, glass, concrete, computers, file cabinets, people, etc. all reduced to dust.
3. First time a non-engineered gravitational collapse ever caused steel to melt.... Metallurgical studies on WTC steel reveal intergranular melting of steel structural building components making solid steel girders appear like Swiss cheese.
4. First time a non-engineered gravitational collapse ever caused concrete to melt.... Guns from WTC 6 now on display at the NYC police museum encased in molten concrete.
5. First time a non-engineered gravitational collapse ever resulted in a eutectic reaction.... A liquid eutectic mixture containing primarily iron and oxygen, rich in sulfur, observed to have attacked steel structural building components.
6. First time a non-engineered gravitational collapse ever occured at "free fall" gravitational acceleration.... WTC 7 observed falling for 2.5 seconds (105 feet) at "free fall" gravitational acceleration.
That's a lot of firsts! Any others?