It's almost impossible to imagine a fire of this magnitude, which began on November 9th, 1872.  More than 770 buildings burned in less than 20 hours, most of them commercial buildings that were previously thought to be fire-proof.  Several problems contributed to fighting the fire - the flu that had stricken most of the horses used to pull the fire engines, the attempts to reduce the fire load by exploding kegs of gunpowder inside of buildings, an inadequate water supply, and the crowds of spectators and looters filling the streets.