This article investigates grassroots mobilization around the 1964 Becker Amendment, which aimed to guarantee the constitutionality of religious exercises in American public schools. The proposed amendment was at the heart of a bitter public debate that followed two landmark Supreme Court rulings banning mandated prayer and Bible-reading. Yet in line with church/state scholarship more broadly, scholars of the Becker Amendment have privileged the voices of the elite, from church leaders to journalists and politicians. This article focuses instead on an extraordinary archive of some 13,000 letters for and against the amendment that were written by ordinary Americans. These letters, which have been overlooked by historians, offer a revealing window into popular opinion concerning religion in schools and the relationship between faith and government. Focusing on the letters shifts our understanding of the school prayer controversy in several ways. It brings to light the central role of women as activists. It shows the kinds of issues that resonated at the community level. The letters also demonstrate the complex role of emotion in driving and shaping the public debate. Finally, close scrutiny of the letters offers a grassroots view of the shifting alliances within the American religious landscape that would help power the rise of the Religious Right.