The cause of the fire that burned 410,203 acres throughout Colusa, Glenn, Lake and Mendocino Counties last year has been determined. 

“After a meticulous and thorough investigation, Cal Fire has determined that the Ranch Fire was caused by a spark or hot metal fragment landing in a receptive fuel bed,” read the press release. “The spark or hot metal fragment came from a hammer driving a metal stake into the ground.”

According to the release, no charges have been filed at this time. 

The fire started in the early after hours of July 27, 2018 near the community of Upper Lake in Mendocino County. 

“The tinder dry vegetation and Red Flag Conditions consisting of strong winds, low humility and hot temperatures caused extreme rates of spread which caused the fire to grow rapidly,” read the press release. 

The fire destroyed 280 structures and resulted in the death of one firefighter and three firefighter injuries. 

The Ranch Fire is currently the largest wildfire in California history, measured by acres burned. This fire was also one of two fires that made up the Mendocino Complex. Combined with the River Fire, the Mendocino Complex burned a total of 459,123 acres, 

During 2018, more than 7,571 wildfires burned over 1.8 million acres of land within the state. 

“Californians must remain vigilant and be prepared for wildfire,” read the press release. 

For more information on how to prepare for wildfires, visit or Cal Fire also offered a free “Ready for wildfire” app available for both iPhone and Android phones. 

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