Located within Balboa Park, the zoo was established during the Panama-California International Exposition of 1916. The zoo was officially granted 140 acres by the city in 1921, with canyons, mesas, and other areas containing animal-specific cages, dens, and corrals. Landscape plans were supplied by landscape architect Nathaniel Slaymaker, while architect Louis Gill designed the zoo’s first buildings and cages. In 1955 Balboa Park’s original Japanese Tea House and Garden were dismantled to make room for the Zoo’s expansion. Shortly afterwards, artist Charles Faust redesigned the zoo’s main exhibits to incorporate some of the world’s earliest moated, cageless enclosures. His exhibits were revolutionary in their approach to recreating natural animal habitats. The landscape architecture firm Jones & Jones created a new master plan for the zoo in 1985 that reorganized the zoo into bioclimates that represent distinct plant and animal communities. In 2004 Estrada Land Planning amended the master plan, calling for the reorientation of the zoo’s entry and the conversion of a surface parking lot into zoological gardens and a greenbelt.
Within the Zoo’s current 100 acres, bioclimate zones ranging from desert to lush tropical areas are dotted with numerous exhibits and connected via meandering paths that conform to the site’s dramatic and complex topography. The approximately 700,000 plants located throughout the grounds form a dense, well-shaded botanical garden that is integrated with the animal exhibits. The San Diego Zoo is within the Balboa Park National Historic Landmark District, established in 1977.