The county is noted for its distinctive Pacific Ocean coastline, Redwood forests, wine production, microbrews, and liberal views about the use of cannabis and support for its legalization. It is estimated that roughly one-third of the economy is based on the cultivation of marijuana.
Mendocino County was one of the original counties of California, created in 1850 at the time of statehood. Due to an initially minor white American population, it did not have a separate government until 1859 and was under the administration of Sonoma County prior to that. Some of the county's land was given to Sonoma County between 1850 and 1860.
The county derives its name from Cape Mendocino (which is actually located in adjacent Humboldt County), which was probably named in honor of either Antonio de Mendoza, Viceroy of New Spain, 1535–1542 (who sent the Juan Rodríguez Cabrillo Expedition to this coast in 1542), or Lorenzo Suárez de Mendoza, Viceroy from 1580 to 1583. Mendocino is the adjectival form of the family name of Mendoza.
Neither Spanish nor Mexican influence extended into Mendocino County beyond establishing two Mexican land grants in southern Mendocino County: Rancho Sanel in Hopland, in 1844 and Rancho Yokaya that forms the majority of the Ukiah Valley, in 1845.
In the 19th century, despite the establishment of the Mendocino Indian Reservation and Nome Cult Farm in 1856, the county witnessed many of the most serious atrocities in the extermination of the Californian Native American tribes who originally lived in the area, like the Yuki, the Pomo, the Cahto, and the Wintun. The systematic occupation of their lands, the reduction of many of their members into slavery and the raids against their settlements led to the Mendocino War in 1859, where hundreds of Indians were killed. Establishment of the Round Valley Indian Reservation in March 30, 1870, did not prevent the segregation that continued well into the 20th century.