The site was formerly part of an agricultural outpost of the Mission San Gabriel called Rancho Santa Anita.
Elias Jackson ("Lucky") Baldwin bought Rancho Santa Anita in 1875. The arboretum was founded in 1947 when the State of California and the County of Los Angeles jointly purchased 111 acres. The Queen Anne Cottage was designed by the father of Baldwin's fourth wife, architect Albert A. Bennett. Plants are organised by geographical region. There is also a Herb Garden, Prehistoric Garden and Aquatic Garden. Parts of the film Jurassic Park were filmed here.