Fairfax is an incorporated town in Marin County, California, United States. Fairfax is located 3.25 miles (5.2 km) west-northwest of San Rafael, at an elevation of 115 feet (35 m). The population is 7,319 at the 2000 census.
According to the United States Census Bureau, the town has a total area of 2.1 square miles (5.5 km²), all of it land.
As of the census of 2000, there were 7,319 people, 3,306 households, and 1,811 families residing in the town. The population density was 3,441.2 people per square mile (1,326.7/km²). There were 3,418 housing units at an average density of 1,607.0/sq mi (619.6/km²). The racial makeup of the town was 91.39% White, 1.16% Black or African American, 0.48% Native American, 1.97% Asian, 0.16% Pacific Islander, 1.53% from other races, and 3.31% from two or more races. 5.71% of the population were Hispanic or Latino of any race.
There were 3,306 households out of which 27.4% had children under the age of 18 living with them, 41.2% were married couples living together, 10.0% had a female householder with no husband present, and 45.2% were non-families. 31.1% of all households were made up of individuals and 7.4% had someone living alone who was 65 years of age or older. The average household size was 2.20 and the average family size was 2.76.
In the town the population was spread out with 19.2% under the age of 18, 4.7% from 18 to 24, 33.5% from 25 to 44, 33.1% from 45 to 64, and 9.5% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 91.9 males. For every 100 females age 18 and over, there were 89.2 males.
The median income for a household in the town was $58,465, and the median income for a family was $68,308. Males had a median income of $51,457 versus $40,815 for females. The per capita income for the town was $34,080. About 4.3% of families and 6.5% of the population were below the poverty line, including 6.6% of those under age 18 and 7.6% of those age 65 or over.
Soils in the Fairfax area mostly belong to the Tocaloma Series as classified by the U.S. Soil Conservation Service. These soils consist of moderately deep, well drained soils on uplands. These soils are typically formed from sandstone and shale and often occur on slopes ranging above 15 percent.
The Coast Miwok Indians occupied stretches along local creeks, spring and seep areas; moreover prehistoric habitations were usually chosen near permanent and seasonal drainages, typically along flat ridges and terraces.
The first post office opened in 1910. Fairfax incorporated in 1931. The town was named for Lord Charles Snowden Fairfax.
Fairfax was the site of the last political duel in California, in 1861. Daniel Showalter and Charles Piercy, both former assemblymen in the state legislature , decided to settle a political dispute at the home of Lord Fairfax, a mutual friend of both. Although Fairfax provided lunch to both men and tried to talk them out of it, they eventually headed to an open field nearby and dueled, with Showalter killing Piercy.