1839
August: Immigrant John Sutter arrives in the California Territory and settles inland at the convergence of the Sacramento and American Rivers. He obtains a fifty-thousandacre land grant from Mexican governor Alvarado and begins building his empire, which he christens New Helvetia, but which is more commonly known as Sutter's Fort. The settlement becomes a major trading hub for the region.

1841
November 4: John Bidwell leads the first group of California pioneers into the San Joaquin Valley after a sixmonth overland journey from Independence, Missouri.

1842
March: Rancher Francisco Lopez finds gold in the San Fernando Hills thirty miles northwest of Los Angeles while digging wild onions. Although prospectors from the immediate area converge on the site, there is not enough gold, or water to extract it, to fuel a major gold rush. By 1845, the site is largely exhausted.

1845
July: James Marshall arrives at Sutter's Fort on a wagon train from...