Environment Natural Disasters 10 of the Worst Wildfires in U.S. History By Bryan Nelson Bryan Nelson Twitter Writer SUNY Oswego University of Houston Bryan Nelson is a science writer and award-winning documentary filmmaker with over a decade of experience covering technology, astronomy, medicine, and more. Learn about our editorial process Updated June 20, 2021 The August Complex fire was a symbol of California's catastrophic 2020 wildfire season. Justin Sullivan / Getty Images Share Twitter Pinterest Email Environment Planet Earth Climate Crisis Pollution Recycling & Waste Natural Disasters Transportation The climate crisis has worsened—and will continue to worsen, scientists warn—the western U.S.'s annual fire season. As the planet warms and exacerbates drought conditions, larger swaths of the country have become more susceptible to rampant blazes. In 2020 alone, Colorado had its second-largest fire on record, more than 1,000,000 acres were torched in Oregon, and California had its worst fire year ever. In total, across the U.S., 10 million acres burned. Of course, wildfires have always been a natural (and beneficial) part of many natural ecosystems, but some are simply catastrophic. Here's a look back at 10 of the worst wildfires in U.S. history. 1 of 10 2020 California Wildfire Season (California) Bloomberg Creative / Getty Images California experienced its worst fire season on record in 2020. A total of 10,431 fires occurred, causing more than 4 million acres to burn. Nearly all of them—save the 563 that were ignited by lightning—were started by humans. The largest wildfire in the country in 2020 (and the largest fire complex in California history) was the August Complex fire. Started by a series of lightning strikes, the fire burned throughout Northern California's Coast Range—including the counties of Glenn, Shasta, Mendocino, Lake, Trinity, and Tehama—eventually joining the Elkhorn Fire. Together, they cloaked nearby San Francisco in thick, red, apocalyptic smoke. The August Complex fire raged from August to mid-November. 2 of 10 The Miramichi Fire (Maine) Drawn on the spot by Capt. Hervey Smyth, etched by Paul Sandby (1731-1809), retouched by P. Benazech / Wikimedia Commons / Public Domain The Miramichi Fire of 1825 was one of the worst forest fires in North American history. Though most of its damage was done in New Brunswick (around the Canadian city of Miramichi), the firestorm also reached well into the U.S. state of Maine. By the time the blaze was dispelled, more than 3 million acres had burned and at least 160 people had been killed. One of the more harrowing survival stories to come out of this event involves the residents along the Miramichi River, who waded for hours in its waters while the fire passed. It is said that they shared the water with livestock and even wild animals, including raccoons, deer, bears, and moose, all trying to escape the flames. 3 of 10 The Great Fire of 1910 (Idaho, Montana, and Washington) U.S. Library of Congress / Wikimedia Commons / Public Domain The Great Fire of 1910, also occasionally referred to as the "Big Burn," scorched more than 3 million acres in Idaho, Montana, and Washington—in all, a total area roughly the size of Connecticut. There were 87 fatalities from the fire, 78 of them firefighters. The handling of the blaze went on to shape the future of the U.S. Forest Service. Immediately after the 1910 fire, the service vowed to fight all wildfires, even ones that are naturally occurring and of no threat to human life or property. The merits of this policy are still debated today, especially by ecologists who insist that some wildfires are necessary for ecosystem health. 4 of 10 The Great Fires of 1871 (Michigan, Illinois, and Wisconsin) U.S. Library of Congress / Wikimedia Commons / Public Domain Four of the worst fires in U.S. history all broke out in the same week—October 8, 1871—across the Upper Midwest. The Great Chicago Fire, which destroyed about a third of the city's valuation at the time and left more than 100,000 residents homeless, stole the headlines, but three other fires were also burning. Holland and Manistee, Michigan, were leveled by the "Great Michigan Fire," while across the state, another destroyed Port Huron. The worst of all was perhaps the Great Peshtigo Fire, which ravaged the Wisconsin countryside and killed more than 1,500—making it the deadliest forest fire in U.S. history. That all of these fires happened simultaneously, over such wide distances, has prompted scientists to suggest that the fires were caused by a shower of meteorites, fragments from the impact of Comet Biela. Others blame the unusual confluence of events on high winds. 5 of 10 2008 California Wildfire Season (California) David McNew / Getty Images California experienced one of the most devastating wildfire seasons of the decade in 2008, when 6,255 fires burned 1.5 million acres of land throughout Northern California, Los Angeles, Santa Barbara, and the Pacific Coast. The largest fire that year was the Klamath Theatre Complex fire, in which 11 fires merged to burn nearly 200,000 acres in Siskiyou County (California's northernmost point). Two firefighters died as a result. Other notable infernos from the 2008 California wildfire season include the Basin Complex fire—the second largest of the year, ignited by a lightning strike near Big Sur—and the Iron Alps Complex fire, which led to 10 fatalities in Trinity County. 6 of 10 The Great Fire (Oregon) A single fire in 1845 destroyed as much land as was burned during the entire 2008 California wildfire season. The Great Fire ravaged 1.5 million acres in northern Oregon, ripping through downtown Portland just two years after it officially became a city. The flames spread across 22 blocks in just 24 hours, destroying hundreds of businesses, houses, and commercial properties. The entire downtown area shifted west as a result of the fire—whose scars can now be seen in what is now known as the Portland Yamhill Historic District. 7 of 10 Taylor Complex Fire (Alaska) At the time of Alaska's Taylor Complex fire, in 2004, it was the largest wildfire on record in the U.S. since 1997. Burning more than 1.3 million acres in eastern Alaska near the Canada border, the complex left both sides of the Taylor Highway ablaze and threatened the gold rush town-turned-tourist attraction Chicken. It was the largest conflagration in Alaska's record-breaking 2004 fire season, which ended up seeing roughly 6.5 million acres of forest scorched—the highest total in U.S. history. The fire occurred on one of the driest and hottest summers on record at the time. It was triggered by lightning strikes and remained active from June to September. 8 of 10 2017 Montana Wildfire Season (Montana) Rebecca L. Latson / Getty Images In 2017, about 2,500 wildfires torched 1.3 million acres of Montana land. Though the year was predicted to bring a "below-average fire season," severe flash droughts made for the perfect conditions for wildfire spreading. According to the Montana DNRC's end-of-year fire report, 46% were caused by lightning strikes and 53% by humans. The biggest blaze of the 2017 Montana wildfire season was the Lodgepole Complex fire, which reached 270,000-some acres of grassland and pine forest in and around Jordan and was active from July to August. It destroyed more than 30 homes and structures. 9 of 10 Thumb Fire (Michigan) Also known as the Great Forest Fire of 1881 or the Huron Fire, the 1881 Thumb Fire is named for its location in Michigan's Thumb region. It spread through the counties of Tuscola, Huron, Sanilac, and St. Clair, taking hundreds of lives and destroying countless structures, largely due to a drought caused by a months-long rain deficit. It torched more than a million acres in less than a day (September 6), altering the landscape of the Thumb region for decades—if not centuries—to come. The 1881 fire cloaked much of the eastern U.S. in smoke, resulting in a pseudo twilight at 12 p.m. For this reason, the following day was dubbed "Yellow Tuesday." The fire led to the formation of the Northern Forest and Protection Association, which was superseded by the U.S. Forest Service in 1905. 10 of 10 2020 Oregon Wildfire Season (Oregon) Nathan Howard / Getty Images Like California, Oregon was also barraged with a surplus of fires in 2020, from the largest Santiam Fire, which left the skies above Salem an eerie shade of red, to the Slater and Devil fires that raged along the California-Oregon border. Altogether, more than a million acres were burned, thousands of homes destroyed, and 11 people killed during Oregon's 2020 wildfire season. Although the fire season technically started in early July, things escalated in September, when especially dry conditions and strong winds caused multiple fires to spread rapidly. According to National Interagency Fire Center statistics, 2,215 fires occurred throughout Oregon in 2017—662 were caused by lightning strikes and 1,553 by humans.