The San Gabriel Valley (Spanish: Valle de San Gabriel), often referred to by its initials as SGV, is one of the principal valleys of Southern California, with the city of Los Angeles directly bordering it to the west, and occupying the vast majority of the southeastern part of Los Angeles County.

Once predominantly agricultural, the San Gabriel Valley today is almost entirely urbanized and is an integral part of the Greater Los Angeles metropolitan area.

More recently, statewide droughts have further strained the San Gabriel Valley's and Los Angeles County's water security.

However, for statistical and economic development purposes, the County of Los Angeles generally includes these three cities as part of the San Gabriel Valley.

Its original location, called Mission Vieja, was near where San Gabriel Boulevard now crosses the Rio Hondo, which is also near the present day Juan Matias Sanchez Adobe.

[15] In 1853, with a contingent of Army Engineers passing through searching for the best route to build a railroad, Geologist William P. Blake observed that the once-extensive vineyards were falling to decay, with fences broken down and animals roaming freely through it.

[16] Following the American Civil War, some 5,000 acres (20 km2) of the East Los Angeles region were owned by an Italian settler from Genoa, Alessandro Repetto.

After Repetto's death in 1885, his brother sold his rancho to a consortium of five Los Angeles businessmen including banker Isaias Hellman and wholesale grocer/historian Harris Newmark for $60,000, about $12 an acre.

These pioneers worked the fields, picked the grapes and citrus fruit, and built part the infrastructure of today's San Gabriel Valley.

Hispanic residents, predominately Mexican Americans, are concentrated in Alhambra, Baldwin Park, City of Industry, El Monte, Hacienda Heights, La Puente, Montebello, Rosemead, San Gabriel, South El Monte, West Covina, Covina, Pomona, and Whittier, with significant populations in Pasadena and South Pasadena.

[29] Several business districts developed to serve their needs creating a collection of Southern California Chinatowns loosely connected along the Valley Boulevard Corridor.

Monterey Park is a microcosm of changing demographics, highlighting Asian American history and evolution in the San Gabriel Valley.

Another ethnic enclave is the Filipino American business district of Little Manila, in West Covina along with an Asian indoor and outdoor shopping center.

[32] The largest populations of Asian Americans in San Gabriel Valley were Chinese, Filipinos, Vietnamese, Korean, Taiwanese, and Japanese.

[33] The San Gabriel Valley is home to the annual Tournament of Roses Parade, which is broadcast live on television on New Year's Day from Pasadena.

[38] Old Pasadena has an active nightlife, a shopping mall, boutiques, outdoor cafés, nightclubs, comedy clubs, and varied restaurants.

It remains an unincorporated district governed by the Los Angeles County Board of Supervisors rather than by a locally elected mayor and city council.

Efforts to complete the freeway were met with fierce opposition, including the possibility of using advanced tunneling technologies to overcome objections by South Pasadena.

[58] The portion connecting the recreation area to the Angeles Crest Highway (State Route 2) has been closed to the public since the early 1970s due to massive damage and rockslides.

General aviation is served by San Gabriel Valley Airport (EMT) in El Monte, and Brackett Field (POC) in Pomona.

The Los Angeles edition of the Hong Kong–based Sing Tao is printed in Alhambra and the newspaper is specifically tailored to the Cantonese-speaking readership.

South Pasadena and Alhambra served as the gloomy backgrounds of a fictional Illinois town of Haddonfield in John Carpenter's 1978 horror film Halloween.

[67] Pasadena's distinctive domed City Hall has doubled as a courthouse or capitol building in countless television commercials and movies, and its South Lake shopping district filled in for Rodeo Drive in Beverly Hills Ninja.

Major studio motion pictures filmed in San Marino include Mr. & Mrs, Smith, Disturbia, Enough, Monster-in-Law, Memoirs of a Geisha, Frailty, Men in Black II, The Hot Chick, One Hour Photo, Anger Management, The Wedding Planner, Starsky & Hutch, Intolerable Cruelty, Mystery Men, Legally Blonde 2, The Nutty Professor, Beverly Hills Ninja, The Sweetest Thing, S1m0ne, Charlie's Angels, Indecent Proposal, and American Wedding.

Prime time television programs filmed within city borders include Felicity, The Office, The West Wing, and Alias.

Forrest Gump (1994), starring Tom Hanks, was partially filmed at East Los Angeles College in Monterey Park.

Multiple locations throughout Monrovia also played the role of the fictitious Rome, WI in the TV series Picket Fences.Pinky's Record Store in Friday; The 90s television show Roswell filmed in Covina, most noticeably the downtown area.

Most recently, the former location of a now closed IKEA in the City of Industry was used to film scenes in the movie Mr. & Mrs. Smith (2005), starring Angelina Jolie and Brad Pitt.

[68] Like much of the Los Angeles region, the San Gabriel Valley enjoys a warm, sunny year-round Mediterranean climate.

Due to the Eastern San Gabriel Valley, (East of State Route 57) being more inland, the area is subject to hotter summers and colder winters.