On March 2, 1945, five Mexican American families and their Jewish American lawyer filed a class-action lawsuit against four school districts in Orange County, California, to end the segregation of ethnic Mexican children. In a shocking decision, the court ruled in favor of plaintiffs, setting a legal and historical precedent in Mendez, et al. v. Westminster School District of Orange County that shook the foundations of Jim Crow America and led to the end of de jure school segregation across the nation.Breaking Down the Walls of Segregation tells the story of how ethnic Mexicans in a relatively unknown agricultural backwater built the unprecedented movement that led to this decision. Beginning in the 1880s, David-James Gonzales details the social and economic history of Orange County, explaining how citrus capitalists, seeking increased market share and profitability, established the walls of segregation to manage ethnic Mexican family labor. By the early 1930s, ethnic Mexicans were segregated into over fifty underserved colonias and barrios. Without training or support from national civil rights organizations, they mobilized against segregation and inequality beginning in the late 1920s. Ethnic Mexican grassroots organizations proliferated throughout the county, intent on engaging in civic affairs and ending anti-Mexican discrimination and segregation. This movement, comprised of immigrants, citizens, parents, children, emerging activists, and their non-Mexican allies, paved the way for the growth of LULAC and nationwide organizing. As an essential part of the "long civil rights movement," the ethnic Mexican struggle against segregation in Orange County illustrates how minoritized groups have historically pushed US social, economic, and political institutions to live up to the nation's founding ideals.