As the United States grew in size, a flux of immigrants started to trickle in from the East.
The governor granted a Swiss immigrant, John Sutter, a large piece of land near today's Sacramento.
He wanted him to build a fort to "prevent the robberies committed by adventurers from the United States, the invasion of savage Indians, and the hunting and trading by companies from the Columbia river".
Sutter named his settlement New Helvetia after his homeland (Helvetia = Switzerland). He had indeed fled debts to find fortune in America, abandoning his wife and 5 children behind.
Far from "keeping the Americans out" however, Sutter provided them shelter as they came in through the California trail.
His fort and the area became a major trade and agricultural hub, and can still be visited today.
The Sutter Fort attracted people who had been on the Oregon or California Trail, which took people west from Missouri.
The Oregon Trail was used by about 400,000 settlers, including farmers, miners, ranchers, business owners and their families. Modern highways like the Interstates 80 and 84 follow parts of it.
The California Trail was used by a trickle of travellers before the Gold Rush. One of the tough parts was crossing the Sierra Nevada, as proved by the Donner Party, who got stuck in winter and resorted to eating each other.
Sutter's Fort provided shelter, supplies and guidance to these new settlers.
The fort however was also a place of extreme brutality.
As in the missions, most of the labor was provided by Native Americans, most of whom were enslaved.
There is evidence of horrific brutality, described by shocked visitors to the fort : children being separated from their mothers, raped, sold or given as gifts to other settlers, workers fed in troughs, sleeping in locked rooms with no sanitation, whipped, jailed, executed...
Killing expeditions were also led to wipe out neighbouring Native American settlements.