A census-designated place (CDP) called Twain Harte is located in Tuolumne County, California, in the United States. Its name is a combination of Mark Twain and Bret Harte, two well-known authors who were born and raised in California. At a height of 3,640 feet, Twain Harte is located in Tuolumne County alongside Highway 108. The CDP has a total area of 3.7 square miles, of which 99.49% is land and 0.51% is water, according to the United States Census Bureau. The Stanislaus National Forest's nearby Lyons Reservoir serves as its municipal water source.

Twain Harte has a climate with lengthy, very cold winters that are rainy and partly cloudy and warm, arid summers that are distinguished by largely clear skies. There are very few occasions when the temperature falls below 22°F or rises above 91°F throughout the year, with a usual range of 31°F to 85°F. The warm season lasts for 3.2 months, from June 12 to September 20, with an average daily high temperature of over 77°F. The hottest month is July, with an average temperature of 84°F. However, the cold season lasts for 3.7 months, from November 20 to March 12, and is distinguished by an average daily high temperature below 55°F. With an average low of 32°F and high of 48°F, December stands out as the coldest month.

Twain Harte has 2,226 people living there as of the 2010 United States Census, putting its population density at 598.6 people per square mile. The population was 91.0% White, 0.2% African American, 1.5% Native American, 1.4% Asian, 0.2% Pacific Islander, and 3.6% of individuals identified as belonging to two or more races. 7.7% of the populace also declared themselves to be Hispanic or Latino. There were no reports of institutionalized or group quarters, and all 2,226 people lived in homes. Of the 1,014 households, 19.5% had children under the age of 18, 53.6% were married pairs of opposite sexes, and 26.9% were single people. The population was slightly more male than female, and the median age was 52.0 years. The percentage of housing that was owner-occupied was 70.7%, and the rental vacancy rate was 12.0%.

A single adult's yearly cost of living in Twain Harte, California, which has a cost of living below the state average of $45,534 but above the national average of $38,433, is about $39,485. Given that the typical home value is $320,000, which is more than the national average, housing is a key component. Due to the significant number of commuters who commute by car, transportation expenditures are relatively expensive at $11,777 per year. The annual cost of health care is $4,039, which is somewhat higher than the national average. The cost of child care for two kids is roughly $11,214, which is less than the state average in California. A single adult's annual food expenses come to about $4,320, yet the average worker in Twain Harte pays taxes that are $6,592 less than the state average.