Calaveras Big Trees State Park, a preserve of Giant Sequoia trees, is located in the county several miles east of the town of Arnold on state highway 4. The uncommon gold telluride mineral calaverite is named for the county.
Mark Twain set his story, "The Celebrated Jumping Frog of Calaveras County", in the county. Each year, the county hosts its County Fair and Jumping Frog Jubilee, featuring a frog jumping contest, to celebrate the association with Twain's story. The celebrated California red-legged frog, feared absent from the county by 1969, was rediscovered in 2003.
As of the census of 2000, there were 40,554 people, 16,469 households, and 11,742 families residing in the county. The population density was 40 people per square mile (15/km²). There were 22,946 housing units at an average density of 22 per square mile (9/km²). The racial makeup of the county was 91.19% White, 0.75% Black or African American, 1.74% Native American, 0.85% Asian, 0.09% Pacific Islander, 2.07% from other races, and 3.31% from two or more races. 6.82% of the population were Hispanic or Latino of any race. 15.7% were of German, 13.0% English, 10.7% Irish, 7.4% Italian and 7.0% American ancestry according to Census 2000. 94.5% spoke English and 4.0% Spanish as their first language.
There were 16,469 households out of which 26.7% had children under the age of 18 living with them, 58.9% were married couples living together, 8.6% had a female householder with no husband present, and 28.7% were non-families. 23.3% of all households were made up of individuals and 10.1% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 2.85.
In the county the population was spread out with 22.8% under the age of 18, 5.5% from 18 to 24, 22.4% from 25 to 44, 31.1% from 45 to 64, and 18.2% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 98.5 males. For every 100 females age 18 and over, there were 95.7 males.
The median income for a household in the county was $41,022, and the median income for a family was $47,379. Males had a median income of $41,827 versus $28,108 for females. The per capita income for the county was $21,420. About 8.7% of families and 11.80% of the population were below the poverty line, including 15.6% of those under age 18 and 6.2% of those age 65 or over.
Calaveras Transit provides service in Angels Camp, San Andreas, and other communities in the county. Intercounty connections are available to Columbia (Tuolumne County), Jackson (Amador County) and Lodi (San Joaquin County)
Calaveras County Airport is a general aviation airport located just southeast of San Andreas.