The fire of 1975
In 1975 the world trade center caught fire. This was two years after the world trade center was completed. The north tower had caught on fire. The fire spread over half of the 11th floor. The fire spread to the other floors by holes in the floor that phone cords went through. The other floors were put out immediately. Fireproofing protected the steel from melting and there was no structural damage to the tower. This event led to the installation of a sprinkler system in both towers. Firefighters claim that had the sprinklers been installed when the tower was built, the fire probably would not have spread as much as it did. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above.