The Great Flood of 1862 was the largest flood in the recorded history of California, Oregon, and Nevada, inundating the Western United States and portions of British Columbia and Mexico. It was preceded by weeks of continuous rains and snows that began in Oregon in November 1861 and continued into January 1862. This was followed by a record amount of rain from January 9–12, and contributed to a flood that extended from the Columbia River southward in western Oregon, and through California to San Diego, as well as extending as far inland as the Washington Territory (now Idaho), the Utah Territory (now Nevada and Utah), and the western New Mexico Territory (now Arizona).
The event dumped an equivalent of 10 feet (3.0 m) of precipitation in California, in the form of rain and snow, over a period of 43 days. Immense snowfalls in the mountains of far western North America caused more flooding in Idaho, Arizona, New Mexico, as well as in Baja California and Sonora, Mexico the following spring and summer, as the snow melted.
The event was capped by an intense, warm storm that melted the heavy snow load that had accumulated during the earlier storms. The resulting snow-melt flooded valleys, inundated or swept away towns, mills, dams, flumes, houses, fences, and domestic animals, and ruined fields. It has been described as the worst disaster ever to strike California. The storms caused an estimated $100 million (1861 US dollars) in damage, roughly equal to $3 billion in 2021. The gove
Why this event still matters
Historical incidents shape the rules that protect people today — building codes, evacuation policy, warning systems and inspection regimes almost always trace back to a specific disaster. Studying Great Flood of 1862 alongside current events is how preparedness improves.
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