The town's name comes from its location near the junction of the North, Middle, and South Forks of the Kaweah River.
Three Rivers is located at 36°27′15″N, 118°53′11″W (36.454212, -118.886466). According to the United States Census Bureau, the CDP has a total area of 45.3 square miles (117.5 km²).
As of the census of 2000, there were 2,248 people, 985 households, and 659 families residing in the CDP. The population density was 49.6 people per square mile (19.1/km²). There were 1,217 housing units at an average density of 26.8/sq mi (10.4/km²). The racial makeup of the CDP was 89.86% White, 0.22% African American, 1.29% Native American, 0.67% Asian, 0.13% Pacific Islander, 3.74% from other races, and 4.09% from two or more races. Hispanic or Latino of any race were 6.58% of the population.
There were 985 households out of which 24.3% had children under the age of 18 living with them, 54.9% were married couples living together, 7.6% had a female householder with no husband present, and 33.0% were non-families. 27.4% of all households were made up of individuals and 12.2% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.75.
In the CDP the population was spread out with 20.9% under the age of 18, 4.6% from 18 to 24, 20.3% from 25 to 44, 32.1% from 45 to 64, and 22.1% who were 65 years of age or older. The median age was 47 years. For every 100 females there were 94.1 males. For every 100 females age 18 and over, there were 94.5 males.
The median income for a household in the CDP was $42,727, and the median income for a family was $48,843. Males had a median income of $39,355 versus $31,875 for females. The per capita income for the CDP was $23,475. About 7.5% of families and 9.8% of the population were below the poverty line, including 14.3% of those under age 18 and 6.4% of those age 65 or over.
Three Rivers was one site of a handful of U.S. boarding schools run by the Hare Krishna movement. These schools, called "gurukulas," were closed by the mid-1980s. Other locations included Los Angeles; Moundsville, W. Va.; and Dallas.
Due to its small population, Three Rivers has only a K-8 school with about 200 children.
The Three Rivers cemetery contains the bodies of nine Rhodesian pioneers who lived in Africa ca. 1900 and fought in several Anglo-African wars:
The Burnhams and the Blicks started a 5,000-acre (20 km2) cattle ranch, La Cuesta, in Three Rivers and built homes there. The scenery at Three Rivers is said to be almost identical to that of the Rhodesian kopje country. La Custa was sold by the John and Judd Blick in 1947 for $90,000.
In the 1960s several local artists held exhibitions in the old Apple House on the North Fork Drive. Some of these artists included Adrian Green, Gene Gray, Caroll Barnes, Frank Treuting, Jean Caulfeild and Pauline Whitsun. Present day artists open their studios every other year for the Three Rivers Artists' Biennial Studio Tour, which was started in 1994 by Elsah Cort (then associated with the Cort Gallery.) As of the year 2009, more than thirty artists are living and working in Three Rivers, including Mona Fox Selph and Jim Entz, who also taught at College of the Sequoias in Visalia, California.
In the state legislature Three Rivers is located in the 18th Senate District, represented by Republican Roy Ashburn, and in the 34th Assembly District, represented by Republican Connie Conway. Federally, Three Rivers is located in California's 21st congressional district, which has a Cook PVI of R +13 and is represented by Republican Devin Nunes.