Brentwood was part of the Rancho San Vicente y Santa Monica, a Mexican land-grant ranch sold off in pieces by the Sepúlveda family after the Mexican-American War.

Modern development began after the establishment of the 600-acre (2.4 km2) Pacific Branch of the National Home for Disabled Soldiers and Sailors in the 1880s. A small community sprang up outside that facility's west gate, taking on the name Westgate. Annexed by the City of Los Angeles on June 14, 1916, Westgate's 49 square miles (130 km2) included large parts of what is now the Pacific Palisades and a small portion of today's Bel-Air. Westgate Avenue is one of the last reminders of that namesake.

The Sunset Fields Golf Club, known as the Brentwood Country Club since 1941, hosted the running part of the modern pentathlon event in the 1932 Summer Olympics.

The preceding statement is incorrect and caused by a confusion of Olympic events & locations. Brentwood Country Club was known as Brentwood Country Club at the time of the 1932 Los Angeles Olympics. It appears as Brentwood Country Club at 590 Burlingame Avenue in the Los Angeles City Directory for 1933, which would have been compiled in 1932.  A 1927 Los Angeles Times article describes the beginning of construction on Sunset Fields Golf Course near Crenshaw Boulevard between Vernon Avenue and Santa Barbara Avenue (now Martin Luther King Jr. Boulevard).

The book, Leimert Park, states, "The Sunset Fields Golf Course in Leimert Park was also the location of another official Olympic venue, the running portion of the modern pentathlon .... The close proximity of the Olympic games to the neighboring community of Leimert Park brought much attention to the development." The Xth Olympiad: Los Angeles, 1932 - Official Report says, "The Cross Country Run of the Modern Pentathlon was held at 9:00 A.M. on the course of Sunset Fields Golf Club of Los Angeles. The distance was 4000 metres, slightly less than two-thirds of which was laid on the fairways of the golf course, and over and through several of the natural washes and gullies to be found on the course. The remainder involved the climbing of a very steep hill, to the level of the Olympic Village, thence down a narrow draw by a winding path and across a wide ditch to the Golf Club property again. The start and finish were a short distance in front of the clubhouse." A map of the various Olympic venues and locations in the same report shows the Olympic Village as being located southwest of the intersection of Vernon Avenue and Crenshaw Boulevard, which lies exactly where Sunset Fields Golf Course was (an area now occupied by the Baldwin Hills Crenshaw Plaza).

The confusion may have arisen because part of the route of the Equestrian Cross Country portion of Modern Pentathlon may have crossed Brentwood Country Club. This event used the route of Phase D of the Cross Country portion of the Equestrian Three-Day Event competition.  Riviera Country Club in Bel-Air, east of Brentwood, served as the headquarters of all Olympic Equestrian Events,  A map in the Official Report shows the equestrian course briefly following Burlingame Avenue in Brentwood. As in 1932, the address of Brentwood Country Club of Los Angeles is still 590 South Burlingame Avenue.

Archer School for Girls maypole tradition

Local traditions include the annual decoration of San Vicente Boulevard's coral trees with holiday lights and a Maypole erected each year on the lawn of the Archer School for Girls, carrying on that set by the Eastern Star Home previously housed there. This building was the exterior establishing shot for the "Mar Vista Rest Home" that provided a key scene in the 1974 film Chinatown.