Mount Bullion (formerly Princeton and La Mineta) is a census-designated place (CDP) in Mariposa County, California, United States, along California State Route 49 in the Mother Lode country of the western Sierra Nevada. The community lies northwest of Mariposa, the county seat, at an elevation of . The population was 154 at the 2020 United States census.
Mount Bullion developed as a Gold Rush-era mining settlement in the 1850s. Originally called La Mineta (Spanish for "little mine"), the community was later renamed Princeton for a nearby mine before receiving its present name in honor of U.S. Senator Thomas Hart Benton, whose nickname "Old Bullion" reflected his advocacy for hard currency policies.
The area that became Mount Bullion was settled during the California Gold Rush, which brought prospectors to the Mother Lode belt along the western slope of the Sierra Nevada beginning in 1849. The community first took the name La Mineta, a Spanish term meaning "little mine." As the nearby Princeton Mine became productive, the settlement was renamed Princeton.
The community received its final name in honor of Thomas Hart Benton, the U.S. Senator from Missouri who served from 1821 to 1851. Benton earned the nickname "Old Bullion" for his staunch support of gold and silver currency over paper money. The name reflected both his monetary convictions and the gold mining that defined the region's economy.
A post office operated at Mount Bullion from 1862 to 1955, with a period of closure during 1887. Its long operation indicates the community's persistence well beyond the initial Gold Rush era, sustained by continued mining activity and ranching in the surrounding foothills.
Mount Bullion sits within the Mother Lode gold belt, a zone of gold-bearing quartz veins extending roughly along the western Sierra Nevada foothills. The Princeton Mine, which gave the community its second name, was among the productive lode mines in the district.
The area is known among mineral collectors for the Mockingbird Mine, near Mount Bullion, which has produced fine specimens of crystalline gold on quartz matrix.
Mount Bullion is in west-central Mariposa County along California State Route 49. It lies northwest of Mariposa, the county seat, and southeast of Bear Valley.
The Mount Bullion CDP has an area of , nearly all of it land. The community sits on a low divide between the headwaters of Agua Fria Creek flowing southeast and the heads of Norwegian Gulch and Green Gulch, which run west to Bear Creek. Both systems drain southwest into the San Joaquin Valley.
Mount Bullion first appeared as a census-designated place in the 2020 census.
The 2020 census reported a population of 154 and a population density of . The racial makeup was 112 (72.7%) White (non-Hispanic), 3 (1.9%) African American, 1 (0.6%) other race (non-Hispanic), and 12 (7.8%) from two or more races (non-Hispanic). Hispanic or Latino of any race were 26 persons (16.9%).
In the California State Legislature, Mount Bullion is in , and in .
In the United States House of Representatives, Mount Bullion is in .
California State Route 49, known as the Golden Chain Highway, passes through Mount Bullion. The highway follows the historic Mother Lode belt and connects the Gold Rush-era communities of the western Sierra Nevada foothills. SR 49 leads southeast to Mariposa and northwest to Bear Valley.