The county's eastern half is the central portion of Yosemite National Park.
There are no incorporated cities in Mariposa County; however, there are three communities recognized as census-designated places for statistical purposes. It also has the distinction of having no permanent traffic lights anywhere in the county.
As of the census of 2000, there were 17,130 people, 6,613 households, and 4,490 families residing in the county. The population density was 12 people per square mile (5/km²). There were 8,826 housing units at an average density of 6 per square mile (2/km²). The racial makeup of the county was 88.93% White, 0.67% Black or African American, 3.51% Native American, 0.71% Asian, 0.13% Pacific Islander, 2.67% from other races, and 3.38% from two or more races. 7.76% of the population were Hispanic or Latino of any race. 17.8% were of German, 13.4% English, 12.7% Irish and 6.7% American ancestry according to Census 2000. 96.0% spoke English and 3.5% Spanish as their first language.
There were 6,613 households out of which 25.6% had children under the age of 18 living with them, 55.8% were married couples living together, 8.0% had a female householder with no husband present, and 32.1% were non-families. 26.5% of all households were made up of individuals and 11.2% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.86.
In the county the population was spread out with 21.6% under the age of 18, 6.9% from 18 to 24, 25.1% from 25 to 44, 29.2% from 45 to 64, and 17.2% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 104.7 males. For every 100 females age 18 and over, there were 105.4 males.
The median income for a household in the county was $34,626, and the median income for a family was $42,655. Males had a median income of $31,194 versus $25,440 for females. The per capita income for the county was $18,190. About 10.5% of families and 14.8% of the population were below the poverty line, including 16.5% of those under age 18 and 9.0% of those age 65 or over.
Mariposa Yosemite Airport is a general aviation airport. The nearest airports with scheduled flights are in Fresno and Merced.