 American trappers began entering northern California in the 1830s.In 1834, American visionary Ewing Young led a herd of horses and mules over the Siskiyou Trail from missions in northern California to British and American settlements in Oregon.Although a small number of American traders and trappers had lived in northern California since the early 1830s, the first organized overland party of American immigrants to arrive in northern California was the Bartleson-Bidwell Party of 1841 via the new California Trail.