Annexed by the City of Los Angeles on June 14, 1916, Westgate's 49 sq mi (130 km2) included large parts of what is now Pacific Palisades and a small portion of today's Bel-Air.

Local traditions include 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.

[citation needed] The State Cal-Fire Authority officially designated Brentwood, from Mulholland down to Sunset Boulevard, a Very High Fire Hazard Severity Zone, due to the long, uninterrupted border of urban-wildlife interface in the hillsides that has resulted in multiple fires over many years, destroying entire neighborhoods and requiring numerous evacuations.

On November 6, 1961, a construction crew working in Sherman Oaks in the San Fernando Valley north of Brentwood on the far side of the Santa Monica Mountains noticed smoke and flames in a nearby pile of rubbish.

More than 300 police officers helped evacuate 3,500 residents during the 12-hour fire, and some 2,500 firefighters battled the blaze, pumping water from neighborhood swimming pools to douse flames.

The fires were the fifth-worst conflagration in the nation's history at the time, burning 16,090 acres (65 km2), destroying 484 homes and 190 other structures and causing an estimated $30 million in damage.

The area south of San Vicente Boulevard features an underground spring which bubbles up into a small creek along "the Gully" near the Brentwood Country Club.

This green belt replaced a Pacific Electric trolley track, and the trees have been named a City of Los Angeles Historic-Cultural Monument.

[6] The vast majority of office space in Brentwood is rented to professional services firms: accountants, lawyers, medical care.

There are three upscale commercial areas: Brentwood Country Mart, Barrington Plaza and the San Vicente Business District, which include restaurants, clothing stores, and other high-end retailers.

A few long time businesses should be noted: Brent-Air Pharmacy, run by the founding Lassoff family from its inception until June 2007, served Brentwood for more than 50 years.

The drug store has been the scene of many famous scandals and, like its defunct West Hollywood cousin Schwab's, is known as the pharmacy to the stars, where many now-notable actors and actresses worked as delivery boys or "candy counter" girls.

The Brentwood Country Mart, near the corner of San Vicente Blvd and 26th Street next to the Santa Monica city limit, is a shopping and food center that first opened in 1948.

Seventy percent of Brentwood residents aged 25 and older had earned a four-year degree by 2000, a high percentage for the city and the county.