Dillon Beach is a census-designated place (CDP) in Marin County, California, United States. Dillon Beach is located 3.25 miles (5.2 km) west of Tomales, at an elevation of 89 feet (27 m). The population was 319 at the 2000 census. Dillon Beach was named after the founder, George Dillon, who settled there in 1858.
Dillon Beach is located near the mouth of Tomales Bay, at.
According to the United States Census Bureau, the CDP has a total area of 2.97 sq mi (7.7 km²), all land.
The first post office at Dillon Beach opened in 1922.
As of the census of 2000, there were 319 people, 155 households, and 103 families residing in the CDP. The population density was 107/sq mi (41.5/km²). There were 415 housing units at an average density of 140/sq mi (54/km²). The racial makeup of the CDP was 94.04% White, 0.31% Black or African American, 0.31% Native American, 2.82% Asian, 0.31% from other races, and 2.19% from two or more races. 0.94% of the population were Hispanic or Latino of any race.
There were 155 households out of which 17.4% had children under the age of 18 living with them, 59.4% were married couples living together, 4.5% had a female householder with no husband present, and 33.5% were non-families. 27.7% of all households were made up of individuals and 10.3% had someone living alone who was 65 years of age or older. The average household size was 2.06 and the average family size was 2.47.
In the CDP the population was spread out with 14.4% under the age of 18, 1.3% from 18 to 24, 18.8% from 25 to 44, 43.6% from 45 to 64, and 21.9% who were 65 years of age or older. The median age was 52 years. For every 100 females there were 95.7 males. For every 100 females age 18 and over, there were 95.0 males.
The median income for a household in the CDP was $47,679, and the median income for a family was $52,000. Males had a median income of $40,714 versus $37,083 for females. The per capita income for the CDP was $39,475. None of the families and 1.3% of the population were living below the poverty line, including no under eighteens and none of those over 64.