Santiago Canyon Fire

The Santiago Canyon Fire of 1889 (previously called the Great Fire of 1889) was a massive wildfire in California, which burned large parts of Orange County, Riverside County, and San Diego County during the last week of September 1889.^[3] The fire reportedly started in Fremont Canyon, a canyon close to what today is Irvine Lake.^[4] Until 2018, it was possibly the single largest wildfire in the recorded history of California,^[1][2] with at least 300,000 acres (1,200 km²) of land burned.^[3] In mid-August 2018, the Ranch Fire in the Mendocino Complex Fire surpassed the Santiago Canyon Fire's assumed acreage.^[5][6]

Assistant Regional Forester (USFS) L.A. Barrett, who wrote a 1935 report on California wildfires, said of it: "I was living in Orange County at the time and well remember the great fire reported herein from September 24 to 26. Nothing like it occurred in California since the National Forests have been administered. In fact in my 33 years in the Service I have never seen a forest or brush fire to equal it. This one covered an enormous scope of country and burned very rapidly."^{[non-primary source needed]}

Conditions leading up to the 1889 fire included a much longer and more severe annual drought than usual, with rains largely ceasing in March and less than 0.4 inches (1 cm) of precipitation being recorded for the 5½ months prior (records from the National Archives). This was coupled with multiple katabatic wind events (known as “northers” or Santa Anas) that month, one of which occurred about 10 days prior and likely added to the dryness of fuels. Temperatures during the week prior remained high and were coupled with several severe fires in San Diego County in which “at least 10,000 acres [40 km²] have burned over, a dwelling house consumed and other property destroyed”.^[7]