History The Great Flood of 1862 was the largest flood in the recorded history of Oregon, Nevada, and California, occurring from December 1861 to January 1862.It was preceded by weeks of continuous rains and snows in the very high elevations 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 which extended from the Columbia River southward in western Oregon, and through California to San Diego, and extended as far inland as Idaho in the Washington Territory, Nevada and Utah in the Utah Territory, and Arizona in the western New Mexico Territory. Large snowfalls in the mountains of the far western United States caused more flooding in Idaho, Arizona, New Mexico, and Sonora, Mexico the following spring and summer as the snow melted.The event was climaxed by a warmer, more intense storm with much more rain that was much more serious, due to the earlier accumulation of snow, now melted by the large turbulent heat fluxes into the snow over the lower elevations of the mountains.Throughout the affected area, all the streams and rivers rose to great heights, flooded the valleys, inundated or swept away towns, mills, dams, flumes, houses, fences, and domestic animals, and ruined fields.In western New Mexico Territory (The boundaries of the New Mexico Territory at the time of establishment (September 9, 1850) contained most of the present-day State of New Mexico, more than half of the present-day State of Arizona, and portions of the present-day states of Colorado and Nevada.), heavy rains fell in late January, causing severe flooding of the Colorado River and Gila River. On January 20, 1862, the Colorado River began to rise, and on the afternoon of January 22, it rose suddenly in three hours from an already high stage nearly 6 feet (1.8 m), overflowing its banks and turned Fort Yuma in California into an island in the midst of the Colorado River.At 1 o’clock on the morning of January 23, the river reached its crest.Jaeger City a mile down river from Fort Yuma, and Colorado City, across the Colorado River from it were washed away.The river overflowed its banks to the extent that there was water 20 feet (6.1 m) deep on a ranch in the low-lying ground just above Arizona City where the Gila River joined the Colorado.The riverside home of steamboat entrepreneur George Alonzo Johnson and the nearby Hooper residence were the only places in the town unharmed because they were built on high ground.Colorado City had to be rebuilt on higher ground after the 1862 flood.The Gila River also flooded, covering its whole valley at its mouth where it met the Colorado from the sand hills on the south to the foothills on the north.Twenty miles (32 km) to the east of Fort Yuma, it swept away most of the mining boomtown of Gila City along with a supply of hay being gathered there to supply the planned advance of the California Column into Confederate Arizona.Further east the road was flooded, buildings and vehicles swept away and traffic was disrupted for some time thereafter by the mud covering the road to Tucson. The great flood in the Gila and Colorado rivers covered their bottom lands with mud. Much of the livestock along the rivers drowned and the crops of the Indians along the river were destroyed. The overflow of the 1862 Colorado River spring flood waters reached the Salton Sink via the Alamo and New Rivers, filling it and creating a lake some 60 miles (97 km) long and 30 miles (48 km) wide.In recent years, the flood has held the attention of the United States Geological Survey and emergency planners, who use it as an example when modelling the impact of a similar event happening in modern-day California.The official name for such an event is “The Arkstorm“, and it is unofficially called “The other big one”.The storm is not an isolated occurrence. Geologic evidence has been found that massive floods, caused by rainfall alone, have occurred in California every 100 to 200 years.