This Dissertation examines the history of the conservative relationship with environmentalism in the United States between 1945 and 1981. In response to recent calls to bring the histories of U.S. political conservatism and environmentalism into conversation with each other, it investigates postwar environmental political history through the lens of partisan and ideological polarization and generates a research agenda for the field. It then contributes three new studies in conservative environmental politics: an analysis of the environmental rhetoric of a national business magazine; the legislative history of the first law to extend the power of the federal government to fight air pollution; and a history of the conservative response to Earth Day. It concludes that conservative opposition to environmentalism in the United States has been both ideological and situational.