California is well known for droughts. But it also had one of the greatest floods in U.S. history.

In 1861, California had been in drought for 20 years.

Most of the state’s residents lived around San Francisco and in the Central Valley.

Ranchers there had been praying for rain for two decades. In November, they finally got it.

First, winter came early, bringing heavy snow to the mountain range that bounds the valley.

In December, temperatures rose, the snow melted and drained into the valley, saturating the soil.

Then the rains came—and didn’t stop for 43 days. Wave after wave of storms rolled in from the Pacific, bringing more than 10 feet of rain and snow.

Creeks became rivers, sweeping entire towns away. Rivers jumped their banks and cut new channels.

But much of the water was trapped in the Central Valley, which became an inland sea, stretching 300 miles north to south, in places 60 miles wide.

It took six months for this inland sea to evaporate and percolate into the ground. But the flood had destroyed a quarter of California’s taxable property and almost forced the state into bankruptcy.

It also wiped out nearly 1 million livestock animals, prompting the Central Valley to move away from ranching to become the agricultural powerhouse we know today.

Superstorms like this come along every 150 to 200 years, and we’ll talk more about them on a future EarthDate.