Humboldt County () is the westernmost county in the U.S. state of California. As of the 2020 census, the population was 136,463. Humboldt County comprises the Eureka–Arcata–Fortuna, California, Micropolitan Statistical Area. The county seat is Eureka.

It is located on the far North Coast of California, about north of San Francisco. It has among the most diverse climates of United States counties, with very mild coastal summers and hot interior days. Similar to the greater region, summers are extremely dry and winters bring substantial rainfall.

Its primary population centers—Eureka, site of College of the Redwoods' main campus, and the smaller town of Arcata, site of California State Polytechnic University, Humboldt—are both adjacent to northern Humboldt Bay, California's second largest natural bay. Area cities and towns are known for hundreds of ornate examples of Victorian architecture.

Humboldt County is a rugged, densely forested, mostly rural region situated within the California Coast and Klamath mountain ranges. It features about of coastline along the Pacific Ocean, more than any other county in the state. With nearly of combined public and private forest in production, Humboldt County alone produces twenty percent of the total volume and thirty percent of the total value of all forest products produced in California.Forestry, Forest Industry, and Forest Products Consumption in California . University of California, Davis: Division of Agriculture and Natural Resources (Adobe Acrobat *.PDF document). Retrieved: March 30, 2008. The county contains over forty percent of all remaining old growth Coast Redwood forests,Area of Old-Growth Forests in California, Oregon, and Washington. – United States Forest Service – USDA. (Adobe Acrobat *.PDF document). Retrieved: November 18, 2007. the vast majority of which are protected or strictly conserved within dozens of national, state, and local forests and parks, totaling approximately .

History The original inhabitants of the area now known as Humboldt County include the Algic-speaking Wiyot and Yurok; Athabaskan peoples including the Hupa, Chilula, Whilkut, Tsnungwe, Mattole, Wailaki and Nongatl; and the Karuk, who speak an isolated language.Van Kirk, Susie, Humboldt County: A Briefest of Histories , Humboldt County Historical Society, May 1999.

Spanish traders made unintended visits to California with the Manila Galleons on their return trips from the Philippines beginning in 1565. The first recorded entry by people of European origin was a landing by the Spanish in 1775 in Trinidad.

The first recorded entry of Humboldt Bay by non-natives was an 1806 visit from a sea otter hunting party from Sitka employed by the Russian-American Company. The party included New England captain Jonathan Winship, Russian supervisors, and Aleut hunters.Humboldt County State Designated Historical Landmarks . California Historical Landmarks. The bay was not visited again by people of European origin until 1849 when Josiah Gregg's party arrived. The following year Douglas Ottinger and Hans Buhne sailed the schooner Laura Virginia into the bay. One of the pioneering passengers, Steven W. Shaw, proposed that the Laura Virginia Association name the bay Humboldt in honor of the naturalist and explorer Alexander von Humboldt. The name was later applied to the county as a whole.

The area around Humboldt Bay was once solely inhabited by the Wiyot Native American tribe. One of the largest Wiyot villages, Tolowot, was located on Tuluwat Island (formerly Indian Island). Founded around 900 BC, it contains a shell shell midden in size and deep. It was the site of the February 26, 1860, massacre of the Wiyot people that was recorded by Bret Harte, then living in Union, now called Arcata. Between 60 and 200 Wiyot men, women, and children were murdered that night in the midst of a religious ceremony. Tolowot is now a restricted site and a National Historic Landmark. In 2019, the Eureka City Council restored ownership of the island to the Wiyot tribe.

Humboldt County was formed in 1853 from a portion of neighboring Trinity County.

State historic landmarks in Humboldt County include Arcata and Mad River Railroad, California's First Drilled Oil Wells in Petrolia, Camp Curtis, Centerville Beach Cross, the city of Eureka, the Victorian town of Ferndale, Fort Humboldt, Humboldt Harbor Historical District, the Jacoby Building, The Old Arrow Tree, Old Indian Village of Tsurai, the Town of Trinidad, and Trinidad Head.

On February 5 and 6, 1885, Eureka's entire Chinese population of 300 men and 20 women were expelled after a gunfight between rival Chinese gangs (tongs) resulted in the wounding of a 12-year-old boy and the death of 56-year-old David Kendall, a Eureka City Councilman. After the shooting, an angry mob of 600 Eureka residents met and informed the Chinese that they were no longer wanted in Eureka and would be hanged if they were to stay in town past 3 p.m. the next day. They were put on two steamships and shipped to San Francisco. No one was killed in the expulsion. Another Chinese expulsion occurred during 1906 in a cannery on the Eel River, in which 23 Chinese cannery workers were expelled after objections to their presence. However, some Chinese remained in the Orleans area, where some white landowners sheltered and purchased food for the Chinese mineworkers until after racial tension passed. Chinese people did not return to the coastal cities until the 1950s.

Geography According to the United States Census Bureau, Humboldt County encompasses , of which is land and is water.

Cape Mendocino is the westernmost point in California (longitude 124 degrees, 24 minutes, 30 seconds). Humboldt Bay, the only deepwater port between San Francisco and Coos Bay, Oregon, is located on the coast at the midpoint of the county.

Humboldt County contains a diversity of plant and animal species, with significant forest and coastal habitats. In coastal areas there are extensive redwood forests.Neil G. Sugihara, Jan W. Van Wagtendonk, Kevin E. Shaffer, JoAnn Fites-Kaufman, Andrea E. Thode (2006) Fire in California's Ecosystems, University of California Press, 596 pages. . A prominent understory shrub is the toyon, whose northern range limit is in Humboldt County.C. Michael Hogan (2008) Toyon: Heteromeles arbutifolia, GlobalTwitcher.com, ed. N. Stromberg

Rivers

Humboldt County's major rivers include (in order of flow – in cubic meters per second – from largest to smallest): Klamath River Eel River Trinity River Mad River

The smaller rivers include Redwood Creek, significant due to amount of its flow; the Van Duzen; the Eel River syncline group composed of the South Fork, the North Fork, and the Salt River; the Mattole, Salmon, Elk, Bear, and Little rivers.

Seismic activity Historically, Humboldt County and the entire far north coast of California have had many earthquakes over 6.0 magnitude. The Mendocino fracture zone is in the area.

The 1992 Cape Mendocino earthquakes were a series of three major earthquakes that occurred off the coast of Cape Mendocino, California on April 25 and 26, 1992, the largest being a 7.2. Ninety-five people were injured and property in the county sustained considerable damage.Cape Mendocino, California Earthquakes , U.S.G.S. (April 25, 1992).

In 2010, a 6.5 magnitude earthquake struck offshore, west of Eureka, resulting in only minor injuries and some structural damage to houses and utilities, and no fatalities reported.Magnitude 6.5 – OFFSHORE NORTHERN CALIFORNIA , U.S.G.S. (January 9, 2010).

On December 20, 2021, a 6.2 earthquake centered off the coast of Cape Mendocino caused minor damage around the county. Exactly one year later on December 20, 2022, a 6.4 magnitude earthquake centered approximately from Ferndale caused greater damage, especially in Rio Dell, as well as two fatalities.

The 2024 Cape Mendocino earthquake was a Mww 7.0 earthquake with an epicenter off the coast of Humboldt County.

The town of Arcata is built on top of an accretionary wedge. This was formed by the subduction of the Gorda plate under the North American plate.

Climate The coastal zone of the county experiences very wet, cool winters and dry, mild foggy summers. In the winter, temperatures range from highs of to lows of . Coastal summers are cool to mild, with average highs of and frequent fog. Coastal summer temperatures range from highs of to lows of . In the populated areas and cities near the coast, the highest temperatures tend to occur at locations just a few miles inland from Eureka and Arcata, in towns like Fortuna, Rio Dell, and smaller unincorporated communities located somewhat further away from Humboldt Bay. In these locations summer highs are . The coastal zone experiences a number of frosty nights in winter and early spring, though snowfall and hard freezes are rare. Coastal winters are cool and wet. Winter rainstorms are frequent, with averages from a year, depending upon elevation.

Inland areas of the county also experience wet, cool winters. Snowfall is common at elevations over throughout the winter months, and is deep enough at higher elevations to have inspired the opening of a small ski lift operation (now defunct) on Horse Mountain, near Willow Creek, for several decades in the late 20th century. Summer displays the sharpest difference between the coastal and inland climates. Inland regions of Humboldt County experience highs of depending on the elevation and distance from the ocean. Occasional summer highs of are common in eastern and southern parts of the county including Orleans, Hoopa, Willow Creek, Garberville, Honeydew, and inland river valleys.

+Average daily maximum and minimum temperatures for warmest and coldest months in selected settlements of Humboldt CountyLocationMonthTemp (°F)Temp (°C)MonthTemp (°F)Temp (°C)Eureka August 64/52 18/11 December 55/40 12/4Arcata September 62/51 17/11 December 54/38 12/3Ferndale August 71/52 22/11 December 56/39 13/4Willow Creek July 94/52 34/11 December 50/35 10/1Garberville August 87/53 31/12 December 49/37 9/3Shelter Cove August 69/53 21/11 January 57/45 14/7Orick August 69/49 21/9 January 52/37 11/2

Demographics

2020 census As of the 2020 census, the county had a population of 136,463. The median age was 39.1 years. 19.5% of residents were under the age of 18 and 19.1% of residents were 65 years of age or older. For every 100 females there were 98.6 males, and for every 100 females age 18 and over there were 97.1 males age 18 and over.

The racial makeup of the county was 71.9% White, 1.4% Black or African American, 6.2% American Indian and Alaska Native, 2.6% Asian, 0.3% Native Hawaiian and Pacific Islander, 5.7% from some other race, and 11.8% from two or more races. Hispanic or Latino residents of any race comprised 13.6% of the population.

68.5% of residents lived in urban areas, while 31.5% lived in rural areas.

There were 56,422 households in the county, of which 25.5% had children under the age of 18 living with them and 28.9% had a female householder with no spouse or partner present. About 31.7% of all households were made up of individuals and 13.0% had someone living alone who was 65 years of age or older.

There were 62,120 housing units, of which 9.2% were vacant. Among occupied housing units, 55.3% were owner-occupied and 44.7% were renter-occupied. The homeowner vacancy rate was 1.4% and the rental vacancy rate was 4.7%.

Racial and ethnic composition