In one way, the twin towers were exceptional, and in another, they were completely characteristic of that moment in American architecture in the late 1960s and early 70s, when a kind of value, aesthetic value, of engineering innovation, as well as a kind of minimalism or economy of expression, in terms of structural engineering, seemed to have a value all its own. Architects and engineers working together in collaboration, as Yamasaki worked with the engineer Les Robertson, was a kind of ideal of the marriage of the arts of design and of construction. And one saw that in other buildings of that particular moment -- of course in Chicago in the John Hancock Tower, or in the Sears Tower, which, soon after the Trade Center topped out, was rising to become and take over the title of the world's tallest. But the principle that drove those buildings up and forward was a kind of implicit belief in the perfection of cooperation of architecture and engineering as a kind of aesthetic economy that balanced the kind of economics of the bottom line, that was so important in skyscraper design.

One looks at the other buildings of that period, like the Sears Tower or John Hancock, and you see an American belief in technology, an ambition to build taller, to be better, to use technology to ascend. Whether it was to shoot for the moon and the space walks, or whether it was to raise the human and the radio and television antenna far above that -- to bring that technology to the top was a part of the belief in a sort of American invention and an advancing world where bigger is better, and technology solves problems rather than creates them.