The county is noted for its wild Pacific Ocean coast and the independent nature of its population.
Mendocino County was one of the original counties of California, created in 1850 at the time of statehood.
According to the U.S. Census Bureau, the county has a total area of 10,044 km² (3,878 mi²). 9,088 km² (3,509 mi²) of it is land and 956 km² (369 mi²) of it is water. The total area is 9.52% water.
As of the census2 of 2000, there are 86,265 people, 33,266 households, and 21,855 families residing in the county. The population density is 9/km² (25/mi²). There are 36,937 housing units at an average density of 4/km² (10/mi²). The racial makeup of the county is 80.76% White, 0.62% Black or African American, 4.76% Native American, 1.20% Asian, 0.15% Pacific Islander, 8.61% from other races, and 3.90% from two or more races. 16.48% of the population are Hispanic or Latino of any race.
There are 33,266 households out of which 31.40% have children under the age of 18 living with them, 48.90% are married couples living together, 11.70% have a female householder with no husband present, and 34.30% are non-families. 27.00% of all households are made up of individuals and 10.40% have someone living alone who is 65 years of age or older. The average household size is 2.53 and the average family size is 3.04.
In the county the population is spread out with 25.50% under the age of 18, 8.10% from 18 to 24, 25.60% from 25 to 44, 27.10% from 45 to 64, and 13.60% who are 65 years of age or older. The median age is 39 years. For every 100 females there are 98.90 males. For every 100 females age 18 and over, there are 97.10 males.
The median income for a household in the county is $35,996, and the median income for a family is $42,168. Males have a median income of $33,128 versus $23,774 for females. The per capita income for the county is $19,443. 15.90% of the population and 10.90% of families are below the poverty line. Out of the total people living in poverty, 21.50% are under the age of 18 and 7.70% are 65 or older.