Topanga State Park in Los Angeles occupies 11,000 acres of the Santa Monica Mountains and is regarded as the largest park within a city. Its landscape was inhabited for thousands of years by the Tongva and Chumash, later becoming part of Rancho San Vicente y Santa Monica under Mexican rule before passing through U.S. claims and homesteading. In the early 20th century, Topanga Canyon developed as a rural retreat, including Trippet Ranch, which later became central to the park. Voter-approved land purchases in 1964 led to the park’s opening in 1974. Today it preserves diverse geology, habitats, wildlife, and a major recreational trail network.