[8] Mendocino County consists wholly of the Ukiah, California Micropolitan Statistical Area (μSA) for the purposes of the U.S. Census Bureau.

It is located approximately equidistant from the San Francisco Bay Area and California/Oregon border, separated from the Sacramento Valley to the east by the California Coast Ranges.

[9] The county is noted for its distinctive Pacific Ocean coastline, its location along California's "Lost Coast", Redwood forests, wine production, microbrews, and liberal views about the use of cannabis and support for its legalization.

Due to an initially minor settler American population, it did not have a separate government until 1859 and was under the administration of Sonoma County prior to that.

[12] The county derives its name from Cape Mendocino (most of 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),[13] or Lorenzo Suárez de Mendoza, Viceroy from 1580 to 1583.

[11][13] 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.

In the first half of the 1850's the California State Legislature established that the boundaries of Mendocino and Trinity Counties was the 40th parallel north.

As of 2023, the District Attorney of Mendocino County is C. David Eyster,[35] the elected Sheriff-Coroner is Matthew C. Kendall [36] and the chief executive officer is Darcie Antle.

The third district, in the northeastern quadrant of the county from Willits north to Laytonville and Covelo, is represented by John Haschak.

However, in the 2016 election, Mendocino County gave Hillary Clinton a reduced margin of victory of any Democrat since Al Gore (though support for third-party candidates more than doubled from 2012).

Federally, Mendocino County is in California's 2nd congressional district, represented by Democrat Jared Huffman.

In 2000, Mendocino County voters approved Measure G, which calls for the decriminalization of marijuana when used and cultivated for personal use.

[47] Measure G passed with a 58% majority vote, making it the first county in the United States to declare prosecution of small-scale marijuana offenses the "lowest priority" for local law enforcement.

On July 3, the Sheriff and District Attorneys offices announced that they would not be enforcing the new regulations for the time being, citing pending legal challenges and conflicts with existing state law.

[51] In April 2009, Sheriff Tom Allman issued his department's medical marijuana enforcement policy, which includes the provisions of Measure B and also cites the California Supreme Court Ruling narrowly defining "caregiver" in the state's medical marijuana law.

[53] On November 4, 2008, Mendocino County voted 63.1% against Proposition 8 which amended the California Constitution to define marriage as a union between one man and one woman.

These four papers have seen a precipitous decline in the size of editorial staff and in coverage over the past several years, in keeping with the nationwide tactics of DFM.

[64] The historic Skunk Train is a heritage railway (that formerly connected Fort Bragg, California with Willits) using steam locomotives.

[65] † county seat "Mendocino" by the Sir Douglas Quintet was released in December 1968 and reached number 27 in the U.S.

Many films and movies have been filmed in and around Mendocino County, including Dying Young, The Russians Are Coming, Overboard, The Dunwich Horror, The Karate Kid Part III, Dead & Buried, Forever Young, Same Time Next Year, Racing with the Moon, Pontiac Moon, and The Majestic.