December 30, 1903 the single deadliest building fire in US history struck the Iroquois Theater at 24-28 West Randolph Street; the conflagration claimed 602 total lives including 571 in just 20 minutes.
The theater had just opened a month earlier and was showing the musical Mr. Bluebeard on the night of the disaster. A lighting arc started the blaze which spread quickly to the backstage and the 300 actors and stage crew fled through giant backstage double doors (only 5 staffers died) which sent a giant Chicago chill wind-fueled fireball into the audience. The orchestra continued to play as comedian Eddie Foy attempted to calm the panicked audience. "A sort of cyclone came from behind," Foy reported. "And there seemed to be an explosion."
Unfinished fire escapes, locked doors, an inoperable stage fire curtain, a lack of fire extinguishing equipment, overlooked fire codes (bribed were involved here (the Chicago way)), and an over packed house of nearly 2,000 patrons only made matters worse, and corpses were soon stacked 10 high around doors and windows.
"The screams of the children for their mothers and mothers for their children I shall carry in my memory to my dying day." -- Frank Slosson, Secretary-Treasurer of the Bain Wagon Works, survivor.
It ranks as the ninth most deadly structure fire of all-time in a list populated by Chinese conflagrations and the Church of the Company fire which killed between 2,000 and 3,000 people in Santiago, Chile in 1863. Not one of the injured survivors or victims' relatives ever collected a cent of damages.
The theater had been billed as "fire-proof" and the outside shell continued to stand after the blaze but was torn torn down in 1926. The Oriental Theater now stands in its place.
A fascinating 33mb PDF of the book Chicago's Awful Theater Horror from 1904 with pictures and first-hand accounts is available here from the U of I library.