Diamond Bar

History

In 1840, José de la Luz Linares received the Mexican land grant Rancho Los Nogales (Ranch of the Walnut Trees) from Governor Juan Alvarado. The land grant included Brea Canyon and the eastern Walnut Valley. Linares died in 1847, and his widow sold a part of the ranch to Ricardo Vejar for $100 in merchandise, 100 calves, and the assumption of her late husband's debts. Vejar also owned the Rancho San Jose to the east, and acquired the rest of Rancho Nogales over the next 10 years. However, Vejar's luck did not last that long. As time wore on – and particularly as the United States government took over California – Rancho Los Nogales was divided and sold into multiple land ranches, the largest of which was the Diamond Bar Ranch. At the time, it was one of the largest working cattle ranches in the western U.S. The entire Diamond Bar Ranch was acquired by the Transamerica Corporation in the 1950s for the purpose of developing one of the nation's first master-planned communities. Transamerica gave the Diamond Bar name to its new community and incorporated the ranch's familiar diamond and bar cattle brand into various logos (many of which are still in use today). The first houses in this development were built in 1959, adjacent to the future location of the Pomona Freeway, which was built through the area ten years later. The town's development and population grew extremely quickly after that. Transamerica oversaw all development of the community through the 1960s. The Transamerica Corporation divested itself of all its real estate ventures in the 1970s and 1980s. As a result, the Diamond Bar project was sold to multiple developers and much of its initial master plan was not implemented during the latter half of its development in the 1980s. The City of Diamond Bar was…

Geography

Diamond Bar's main road, Diamond Bar Boulevard, runs along the bottom of the valley that eventually becomes Brea Canyon, and housing developments overlook the boulevard on both sides from surrounding hills. The city lies roughly between the ends of the Chino Fault and the Whittier Fault, both part of the Elsinore Fault Zone. Positioned in the southeastern corner of the San Gabriel Valley in eastern Los Angeles County, Diamond Bar is approximately east of Downtown Los Angeles. Neighboring communities include Walnut, Rowland Heights, and Pomona. Diamond Bar is also adjacent to the Inland Empire region, with Chino Hills directly to the east, and to the south of Diamond Bar lie the cities of Brea and La Habra in Orange County. According to the United States Census Bureau, the city has a total area of , with no significant bodies of water. Both the CA-60 Freeway and the CA-57 Freeway run through Diamond Bar. the I-10 Freeway is just north of the city and CA-71 is just east of the city. Major thoroughfares include Grand Avenue, Diamond Bar Boulevard, Pathfinder Road, Golden Springs Drive, and Brea Canyon Road.

Race & ethnicity

Most-observed species

• House Finch

  Haemorhous mexicanus (P.L.Statius Müller, 1776) · Aves
  39,048
• Mourning Dove

  Zenaida macroura (Linnaeus, 1758) · Aves
  32,006
• Black Phoebe

  Sayornis nigricans (Swainson, 1827) · Aves
  31,729
• Lesser Goldfinch

  Spinus psaltria (Say, 1822) · Aves
  30,577
• California Towhee

  Melozone crissalis (Vigors, 1839) · Aves
  28,078
• Anna's Hummingbird

  Calypte anna (R.Lesson, 1829) · Aves
  27,343
• Northern Mockingbird

  Mimus polyglottos (Linnaeus, 1758) · Aves
  26,416
• Yellow-rumped Warbler

  Setophaga coronata (Linnaeus, 1766) · Aves
  24,149

Largest nearby schools

• Diamond Bar High
  High · Diamond Bar · 2,557 students · 26.6:1 ratio
• Options For Youth - Duarte Inc
  High · City Of Industry · 2,354 students · 28:1 ratio
• Glendora High
  High · Glendora · 2,273 students · 25:1 ratio
• Claremont High
  High · Claremont · 2,256 students · 24.8:1 ratio
• Walnut High
  High · Walnut · 2,158 students · 23.2:1 ratio
• John A. Rowland High
  High · Rowland Heights · 2,025 students · 24.4:1 ratio
• West Covina High
  High · West Covina · 1,887 students · 21.4:1 ratio
• Bonita High
  High · La Verne · 1,883 students · 25.8:1 ratio

Most recent

• M 3.81008714964485 — 2026-09-30
  4 km SE of Piru, CA
• M 3.55404092525043 — 2026-09-27
  7 km WSW of Hermosa Beach, CA
• M 2.94 — 2026-09-17
  4 km SSE of Compton, CA
• M 2.56 — 2026-09-13
  27 km SSE of Malibu, CA
• M 2.65 — 2026-09-12
  4 km E of Lennox, CA
• M 3.31 — 2026-09-12
  26 km ESE of Avalon, CA