This article traces the basic qualities of big science and applies them to the history of what I envision as “big religion.” Big religion offers a model for understanding several developments in mid-century American religious history, including religious revival within the mainline churches and synagogues, an evangelical resurgence, and various forms of backlash as well. Like big science, big religion peaked during the postwar era (though it built on earlier foundations) and is characterized by heightened institutionalization, professionalization, centralization of knowledge, government entanglements, and public support, as well as opposition. With big science as a guide, the concept of big religion offers historians of American religion an analogous manner of understanding the development of institutions, individuals, and movements within American religion, as well as responses and backlashes against them, as part of the same overarching phenomenon.