Diamond Bar is a city in the San Gabriel Valley of eastern Los Angeles County, California, set on rolling hills near the junction of the Pomona Freeway (State Route 60) and the Orange Freeway (State Route 57). Its name comes from the "diamond over a bar" branding iron registered in 1918 by rancher Frederic E. Lewis, a reminder of the cattle-ranching era that preceded the modern suburb. The city's modern form began in the 1950s, when the Transamerica Corporation acquired the ranch and began developing it as a master-planned community. Over the following decades, houses, schools, and commercial corridors replaced pastureland, and Diamond Bar incorporated as a city in 1989. Today it is a mature suburb of roughly 55,000 residents, with a notably diverse population — over half of residents identify as Asian American, reflected in the area's restaurants, markets, and community institutions. Diamond Bar is best understood as a planned, family-oriented suburb positioned as a gateway between the San Gabriel Valley and the Inland Empire. Its signature neighborhood, Diamond Bar Country Estates — known locally as The Country — is a gated enclave of custom homes with private equestrian trails and sweeping views of the Walnut and Pomona valleys, carrying the area's equestrian heritage into the present. The rest of the city unfolds in conventional tracts of single-family homes with neighborhood parks and schools. The city's anchor institutions are its schools. The Walnut Valley Unified School District, which serves Diamond Bar along with neighboring Walnut, ranks among the top-performing districts in California, and its schools are a primary reason families choose the area. Combined with its freeway position, Diamond Bar suits households seeking strong schools, hillside scenery, and reach to employment across four counties.