Image of the WTC from the Battery Park area.
The WTC represented a symbol of the United States. These towers were within walking distance of the very ground that that greeted and welcomed the ancestors of almost 2/3 of all current, living Americans. It soared above the Wall Street area, the dynamo that is the American economy. The terrorists knew what symbol to strike at.

Designed by Minoru Yamasaki, a diminutive architect who was only 5'2" himeself, and built in 1973 with an eye for the our bicentenial celebrations in 1976, the WTC is *the* pre-eminent icon of America, along side the Statue of Liberty and the Empire State Building.