The transition from agricultural to residential use of today's Cheviot Hills area happened around the time the City of Los Angeles annexing much of the former Rancho Rincón de los Bueyes through t he May 16, 1923, "Ambassador Addition." On October 10, 1922, the City Council rejected the first annexation petition (along with Laurel Canyon's) because " the petitions did not include the districts' sharing in the carrying charges of the recently approved $12,000,000 sewer bond issue. " On March 20, 1923, electors in the new territory chose to join Los Angeles, and the City Council annexed it the next day .
The Ambassador name likely came from the fact that a large section in the northwest held the Ambassador Hotel's golf course, which had opened on the land in July 1921 . "Ambassador" was also used for the July 1923 Ambassador Park subdivision in the northeast portion of the former Rancho la Ballona – an area already annexed to Los Angeles with the May 22, 1915, Palms Annexation .
In the far left, Lot A (Tract 843) of José de Arnaz' subdivision of Rancho Rincón de los Bueyes became the larger section of the Country Club Highlands subdivision . Immediately east, Arnaz' Lots B and C were the Ambassador Hotel's ​Rancho Country Club, while Lot D and the northern portion of Lot E were Hillcrest Country Club. Beneath them, most of Lot E of Arnaz' earlier subdivision became the Monte Mar Vista subdivision . To the west, ​​ Tract Number 1938, a subdivision of Francisco Higuera's Lot A in the Rancho Rincón de los Bueyes, would become the Cheviot Hills subdivision.