Two fires, one night: the one that killed the most is the one we forgot
8 October 1871: two fires started the same night, 250 miles apart.
Chicago (8-10 Oct): about 300 dead, 17,000 structures destroyed, 100,000 left homeless. The legend that grew around it includes Mrs. O'Leary's cow, which the reporter Michael Ahern admitted he made up (retracted 1893). We kept the cow anyway.
Peshtigo, Wisconsin (8 Oct): 1,200 to 2,500 dead, the deadliest wildfire in recorded history, at least five times Chicago's toll. It is largely forgotten. Among the first things to burn were the telegraph lines to Green Bay, so the town that suffered most could not report it. The fire cut its own dispatch.
Sources: Wikipedia, “Peshtigo fire” (date; fatality range 1,200-2,500; “deadliest wildfire in recorded history”; “killed at least five times as many people”; telegraph lines) and “Great Chicago Fire” (about 300 dead; 17,000 structures; Ahern retraction).
One night. The record kept both. History kept one.