Tuolumne County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county were given to Stanislaus County in 1854 and to Alpine County in 1864.
According to the U.S. Census Bureau, the county has a total area of 5,891 km² (2,274 mi²). 5,790 km² (2,235 mi²) of it is land and 101 km² (39 mi²) of it is water. The total area is 1.71% water.
As of the census2 of 2000, there are 54,501 people, 21,004 households, and 14,240 families residing in the county. The population density is 9/km² (24/mi²). There are 28,336 housing units at an average density of 5/km² (13/mi²). The racial makeup of the county is 89.45% White, 2.10% Black or African American, 1.82% Native American, 0.72% Asian, 0.17% Pacific Islander, 2.89% from other races, and 2.84% from two or more races. 8.16% of the population are Hispanic or Latino of any race.
There are 21,004 households out of which 26.10% have children under the age of 18 living with them, 54.40% are married couples living together, 9.60% have a female householder with no husband present, and 32.20% are non-families. 26.00% of all households are made up of individuals and 11.70% have someone living alone who is 65 years of age or older. The average household size is 2.36 and the average family size is 2.82.
In the county the population is spread out with 20.70% under the age of 18, 7.60% from 18 to 24, 25.30% from 25 to 44, 27.90% from 45 to 64, and 18.50% who are 65 years of age or older. The median age is 43 years. For every 100 females there are 111.50 males. For every 100 females age 18 and over, there are 112.20 males.
The median income for a household in the county is $38,725, and the median income for a family is $44,327. Males have a median income of $35,373 versus $25,805 for females. The per capita income for the county is $21,015. 11.40% of the population and 8.10% of families are below the poverty line. Out of the total people living in poverty, 16.20% are under the age of 18 and 4.00% are 65 or older.