The Iroquois Theater Fire goes down in history as the single deadliest structural fire in US history, due mainly to disregard for fire safety regulations.
Among the many mistakes that led to the deaths of 602 theater-goers on 30 December 1903 were the structural flaws of the Iroquois Theater itself. The Iroquois Theater did not comply with contemporary fire codes. Its rooftop vents were incomplete, causing many to die from smoke inhalation when fire broke out during a matinee performance. Fire exits in the theater were unfinished and badly placed; the fire doors were difficult to open, and were hidden behind curtains. Most of the lobby doors were locked when the fire broke out; patrons in the balcony area of the theater found themselves trapped by locked gates on the balcony stairs.
In the wake of the Iroquois Theater Fire, fire codes in the US and Europe were reformed. The new laws stipulated that fire exits be clearly marked, and hinged so that they could be opened from inside or out. The Von Duprin company invented the first panic exit device following the Iroquois Theater Fire; this device is still used in high-occupancy structures today.