San Dimas is a city in the San Gabriel Valley of Los Angeles County, California, set against the foothills of the San Gabriel Mountains near the valley's eastern edge. Its population was 34,924 at the 2020 census. The community's origins reach back to the 1800s, when the area was known as Mud Springs for the marshy ground nearby; it was incorporated as the City of San Dimas in 1960, taking its name from San Dimas Canyon above the townsite. San Dimas occupies a transitional position between the San Gabriel Valley and the neighboring Pomona Valley, giving it a foothill setting that distinguishes it from the flatter communities to the south. The city's downtown carries a distinctive Western theme — a nod to its early agricultural and citrus-growing heritage — and the community maintains a deliberate small-town identity within the larger Los Angeles basin. Education and recreation define much of local life. The Bonita Unified School District, headquartered in San Dimas, serves the city and neighboring La Verne, and the area is within reach of Citrus College and Cal Poly Pomona. Frank G. Bonelli Regional Park, wrapped around Puddingstone Reservoir, is the city's outdoor centerpiece, offering boating, fishing, trails, and open space, while San Dimas Canyon and the San Gabriel Mountains rise immediately to the north. Transportation links keep the city connected: the Foothill Freeway (Interstate 210) runs along the city's northern edge, and a Metrolink station on the San Bernardino Line provides commuter rail into Los Angeles and the Inland Empire. With its foothill location, family-oriented neighborhoods, and strong school district, San Dimas appeals to households seeking a quieter San Gabriel Valley setting with freeway and rail access to the broader region.