Since the publication fifty years ago of Robert N. Bellah's classic article “Civil Religion in America,” the concept of civil religion has provoked continuing debates among scholars who study religion and American culture. This essay is a contribution to these debates and an attempt to move beyond them. It considers American civil religion as theory and as practice, examining its meaning through an investigation of how it functioned at an important and too little studied point in its past. Arguing that civil religion is both a cultural and a political construct, it shows how at the close of World War I, a loosely linked network of civic, military, and patriotic groups came together to create a sacralized form of patriotic nationalism and incorporate it into the American civil religious tradition. Contending that the relationships between civil religion and more conventional forms of organized religion are often close and at times contentious, it examines how religious bodies of the time were instrumental in supporting this process and intractable in resisting it. Proposing that civil religion can come in a variety of sometimes competing versions, it discusses the conflicts over civil religious practices that ensued within American churches during the next decade, relying on reports from the time to describe how these conflicts divided church leaders, denominations, and congregations. Finally, working from the premise that civil religious beliefs, symbols, and rituals are invariably involved in the political process, it examines how they became increasingly used for partisan purposes over the course of the decade, raising issues about the relationship between church and state. In closing, it comments on the enduring character of civil religion, and speculates on its continuing importance for American religion and politics.