The North Tower Survived A Serious Fire in 1975:
Seldom mentioned in the literature about the September 11th attack is the fact that the North Tower experienced a serious fire in 1975, when it was only sparsely occupied. On February 13, 1975, a fire, set by a custodian turned arsonist, started on the 11th floor and spread to limited portions of six other floors, burning for three hours. Several fire suppression systems that were later installed in the towers were not present at the time, including sprinklers, elevator shaft dampers, and electrical system fireproofing.
The fire, which broke out just before midnight, did not kill anyone but forced the evacuation of fifty people, consisting mostly of maintenance staff. The captain of Engine Co. 6 described the suppression effort as “like fighting a blow torch.” One hundred thirty-two firefighters fought the fire, which burned primarily on the 11th floor. Sixteen men were treated for smoke inhalation. The New York Times reported that “flames could be seen pouring out of the 11th-floor windows” on the tower’s east side, but described damage to the tower’s core as “apparently confined to electrical wiring.” The fire spread to portions of the core beyond the 11th floor via telephone cables in a cable shaft.
On the day after the blaze, Fire Commissioner John T. O’Hagan called for the installation of sprinkler systems in the towers. Eventually sprinkler systems were installed throughout the Twin Towers.
Although the data on this fire is limited — there apparently being no publicly available photographs of it.