“Gold! Gold from the American River!” Samuel Brannan walked up and down the streets of San Francisco, holding up a bottle of pure gold dust. His triumphant announcement, and the discovery of gold at nearby Sutter’s Mill in 1848, ushered in a new era for California—one in which millions of settlers rushed to the little-known frontier in a wild race for riches.

But though gold spelled prosperity and power for the white settlers who arrived in California in 1849 and after, it meant disaster for the state’s peaceful indigenous population.

In just 20 years, 80 percent of California’s Native Americans were wiped out. And though some died because of the seizure of their land or diseases caught from new settlers, between 9,000 and 16,000 were murdered in cold blood—the victims of a policy of genocide sponsored by the state of California and gleefully assisted by its newest citizens.

California’s genocide is one of the most heinous chapters in the state’s troubled racial history, which also includes forced sterilizations of people of Mexican descent and discrimination and internment of up to 120,000 people of Japanese descent during World War II. But before any of that, one of the new state’s first priorities was to rid itself of its sizable Native American population, and it did so with a vengeance.

California’s native peoples had a long and rich history; hundreds of thousands of Native Americans speaking up to 80 languages populated the area for thousands of years. In 1848, California became the property of the United States as one of the spoils of the Mexican-American War. Then, in 1850, it became a state. For the state and federal government, it was imperative both to make room for new settlers and to lay claim to gold on traditional tribal lands. And settlers themselves—motivated by bigotry and fear of Native peoples—were intent on removing the approximately 150,000 Native Americans who remained.

“Whites are becoming impressed with the belief that it will be absolutely necessary to exterminate the savages before they can labor much longer in the mines with security,” wrote the Daily Alta California in 1849, reflecting the prejudices of the day.

They were assisted by the government, which considered the so-called “Indian Problem” to be one of the biggest threats to its sovereignty. The legal basis for enslaving California’s native people was effectively enshrined into law at the first session of the state legislature, where officials gave white settlers the right to take custody of Native American children. The law also gave white people the right to arrest Native people for minor offenses like loitering or possessing alcohol and made it possible for whites to put Native Americans convicted of crimes to work to pay off the fines they incurred. The law was widely abused and ultimately led to the enslavement of tens of thousands of Native Americans in the name of their “protection.”

This was just the beginning. Peter Hardenman Burnett, the state’s first governor, saw indigenous Californians as lazy, savage and dangerous. Though he acknowledged that white settlers were taking their territory and bringing disease, he felt that it was the inevitable outcome of the meeting of two races.

“That a war of extermination will continue to be waged between the races until the Indian race becomes extinct must be expected,” he told legislators in the second state of the state address in 1851. “While we cannot anticipate this result but with painful regret, the inevitable destiny of the race is beyond the power or wisdom of man to avert.”

Burnett didn’t just refuse to avert such a conflict—he egged it on. He set aside state money to arm local militias against Native Americans. The state, with the help of the U.S. Army, started assembling a massive arsenal. These weapons were then given to local militias, who were tasked with killing native people.

State militias raided tribal outposts, shooting and sometimes scalping Native Americans. Soon, local settlers began to do the killing themselves. Local governments put bounties on Native American heads and paid settlers for stealing the horses of the people they murdered.

“By demonstrating that the state would not punish Indian killers, but instead reward them,”writes historian Benjamin Madley, “militia expeditions helped inspire vigilantes to kill at least 6,460 California Indians between 1846 and 1873.” The U.S Army also joined in the killing, Madley notes, killing at least 1,600 native Californians.

Large massacres wiped out entire tribal populations. In 1850, for example, around 400 Pomo people, including women and children, were slaughtered by the U.S. Cavalry and local volunteers at Clear Lake north of San Francisco. One of the few survivors was a six-year-old girl named Ni’ka, who stayed alive by hiding in the lake and breathing through a reed.

Meanwhile, white settlers and the California government enslaved native people and forced them to labor for ranchers through at least the mid-1860s. Native Americans were then forced onto reservations and their children forced to attend “Indian assimilation schools.”

An estimated 100,000 Native Americans died during the first two years of the Gold Rush alone; by 1873, only 30,000 indigenous people remained of around 150,000. According to Madley, the state spent a total of about $1.7 million—a staggering sum in its day—to murder up to 16,000 people.

Today, despite all odds, California has the United States’ largest Native American population and is home to 109 federally recognized tribes. But the state’s treatment of native peoples during its founding days—and the role the slaughter of Native Americans played in establishing California’s prosperity—is little known today. California only apologized for the genocide it carried out against its indigenous residents in 2019.