American Airlines Flight 11 crashed into the North Tower (1 WTC), and United Airlines Flight 175 crashed into the South Tower (2 WTC).

The height of WTC 1 was 1,368 ft (417 meters) and WTC 2 was 1,362 ft (415 meters)

While there is a wide range of possible explanations for the collapse of the South Tower (2 WTC) before the North (1 WTC), it is believed that the lower impact of the plane on the tower (a full 15 stories under the same point on 1 WTC) and the passing of shrapnel and parts of the plane through three of four floor beams weakened the structure at an accelerated rate and brought 2 WTC down before its counterpart.

the wtc was made of glass and steel

WTC is what World Trade Center stands for.