In this project, I investigated whether Balboa Park, a 1,200 acre major urban park located in San Diego, California, represents an example of modernism in landscape architecture. Landscape architecture is the design of open spaces for public recreation, social-bonding, ecology and education. It is a multi-disciplinary field which embraces science and human health. The study of modernism of Balboa Park is important not only to designers and scholars, but also to people in general, since one of the most essential contributions of modern landscape architecture to contemporary life is the emphasis that landscapes are for the public, a fundamentally democratic ideal developed at a time when gardens were historically the privilege of the rich minority. First established in 1868, Balboa Park has gone through considerable changes, including during the Panama-California Exposition in 1915. As a 1,200 acre public park, which is early double the size of New York’s Central Park, Balboa Park is a crucial open space for not only the city of San Diego, but also the nation. A modern landscape architecture provides space for public recreation, offers space for public gathering and improves the urban ecology. So, it is valuable to examine whether Balboa Park represents a transition to modern landscape architecture. In order to investigate my hypothesis, which is that Balboa Park is a modern landscape architecture, I engaged the work of several scholars, including Marc Treib, who defines modernism using several “axioms of a Modern Landscape Architecture”. I tested several axioms on Balboa Park, such as “a denial of historical styles”, “landscapes are for people” and so on. Also, I compared Balboa Park to other examples of parks in California from the same time period to prove the modernism of Balboa Park.