San Bernardino County History: The Flood of 1862 – Welcome to San Bernardino County

Downtown Sacramento following the Flood of 1862.

From December 1861 through February 1862, a series of powerful storms driven by atmospheric rivers produced nearly continuous rain in California and surrounding regions. The Santa Ana River flooded and destroyed many farms along its banks.

River settlements throughout California were inundated. Among the hardest hit was the town of Agua Mansa, which is located near present-day Colton. Once the largest settlement in San Bernardino County, Agua Mansa had prospered for nearly 20 years before the 1862 flood, which swept away many of its adobe buildings.

The destruction was devastating statewide. One quarter of California’s economy was impacted, forcing the state into bankruptcy. Enormous regions were transformed into inland seas for an estimated six months, and thousands of lives were lost.

Large brown lakes formed on the normally dry plains in the Los Angeles basin, even covering vast areas of the Mojave Desert. In and around Anaheim, floodwaters of the Santa Ana River created an inland sea up to four feet deep, stretching nearly four miles from the river and lasting for a month.

The disaster even disrupted the inauguration day of California Governor Leland Stanford. On Jan. 10, 1862, floodwaters swept through Sacramento, which forced Stanford to travel from his residence to the capitol building by rowboat to be sworn into office.

Only in recent years have advances in science and technology allowed researchers to better understand the potential scale of future storms. Using sophisticated weather models and expert analysis, the U.S. Geological Survey developed the ARkStorm Scenario, which was modeled after the catastrophic floods of 1861-62.

The scenario hypothesizes that if a similar flood were to occur again, it could cause over $725 billion in damage and impact a fourth of all homes in California. The project aims to raise awareness of the very real threats that extreme storms pose to human life, property and ecosystems.

The information in this historical feature was originally part of a video series produced by the Assessor-Recorder-County Clerk’s office.

Additional County Update News – November 6, 2025