In 1821, Mexico seceded from the Spanish Empire and took California with it.
California was still very remote, with only a trickle of immigration by boat.
When the Mexicans lifted a ban that the Spanish had against trading with other powers, English, Russian and American ships flooded into California.
The number of ships rose from 2 to 25 ships per year.
They would come from as far out as Boston, navigating 14,000 miles through the Cape Horn.
The main port was Monterey, where goods were taxed up to 100%.
You can still see the Custom House today, as well as the Larkin House, built for the first American consul to Mexico, whose style quickly spread throughout the state.
The Mexicans abolished the mission system.
Land and cattle were supposed to go to Native Californians who had worked in the missions.
But in effect, these were given to friends and family of the governors.
This period was the Golden Age for the Californian ranchos.
Around 14,000 square miles of land were handed out to around 500 ranchers, who became rich through the export of hides and cattle fat.
You can still visit the Rancho Petaluma Adobe today.
It was one of the largest ranches in Northern California, employing around 2,000 people, mostly Native Americans, and had around 10,000 cattle.
Northern California at that time was still sparsely populated.
Immigrant children born in California at that period became known as Californios.