Like many American cities, Los Angeles was built upon real estate speculation, mind-boggling boosterism, and war. World War II diversified and expanded the city’s industrial sector; Cold War defense contracts sustained Southern California’s automobile, tire, chemical, and aerospace industries for much of the twentieth century. Oil under residential subdivisions and commercial centers fueled the Pacific fleet. Los Angeles’ industries and business organizations consciously used their contributions to military preparedness to cement their political influence, and to protect themselves from regulation and labor activism. These political phenomena are, perhaps, the most significant aspect of the urban environmental history of World War II in the United States because American cities experienced the environmental impact of World War II primarily through industrial production and its legacies, and because regulating industry is such a critical component of American politics.