On the night of October 8, 1871, Chicago was a wooden tinderbox waiting for a spark. While popular history immortalized Mrs. O'Leary's barn on DeKoven Street as ground zero, a strange secondary crisis unfolded almost simultaneously across town.
Amid the bone-dry autumn air and howling winds, reports emerged of a separate, sudden blaze igniting inside a warehouse packed to the brim with damp straw mattresses. Straw packed tightly in unventilated spaces is notorious for spontaneous combustion due to heat generated by fermenting microorganisms. On this chaotic night, as fire crews responded to initial calls, this independent mattress warehouse fire broke out nearby, creating a deadly distraction and exhausting local firefighting resources right before the main inferno swept through the city center.
Witnesses and fire investigators marveled at the sheer bad luck of the timing. The damp organic bedding material ignited itself via internal chemical heat at the exact hour the city faced its greatest external threat. The coincidence fueled decades of wild rumors, ranging from atmospheric gas anomalies to coordinated arson, but thermal science points to a classic case of biological spontaneous heating.
The straw mattress blaze remains one of the most obscure, tragic coincidences in American urban history, demonstrating how micro-scale biology and macro-scale disaster aligned to burn Chicago to the ground.