Almost all US cities are controlled by real estate and development interests, but Santa Cruz, California, is a deviant case. An unusual coalition of socialist-feminists, environmentalists, social-welfare liberals, and neighborhood activists has stopped every growth project proposed by landowners and developers since 1969, and controlled the city council since 1981. Even after a 1989 earthquake forced the city to rebuild its entire downtown, the progressive elected officials prevailed over developers and landowners. Drawing on hundreds of primary documents, as well as original, previously unpublished interviews, The Leftmost City utilizes an extended case study of Santa Cruz to critique three major theories of urban power: Marxism, public-choice theory, and regime theory. Santa Cruz is presented within the context of other progressive attempts to shape city government, and the authors’ findings support growth-coalition theory, which stresses the conflict between real estate interests and neighborhoods as the fundamental axis of urban politics. The authors conclude their analysis by applying insights gleaned from Santa Cruz to progressive movements nationwide, offering a template for progressive coalitions to effectively organize to achieve political power.