Ben Fallaw argues that previous scholarship has not appreciated the pervasive influence of Catholics and Catholicism on postrevolutionary state formation. By delving into the history of four understudied Mexican states, he is able to show that religion swayed regional politics not just in states such as Guanajuato, in Mexico's central-west "Rosary Belt," but even in those considered much less observant, including Campeche, Guerrero, and Hidalgo. Religion and State Formation in Postrevolutionary Mexico reshapes our understanding of agrarian reform, federal schooling, revolutionary anticlericalism, elections, the Segunda (a second Cristero War in the 1930s), and indigenism, the Revolution's valorization of the Mesoamerican past as the font of national identity.