In the ninety-year period between the start of the American Revolution and the end of the Civil War, American Protestantism underwent a profound transformation. Protestant churches and ministers engaged on both sides of the revolutionary struggle and argued over the relationship between church and state in constitutional deliberations. Religious liberty emerged as an article of faith; religious populism grew; and new Protestant denominations proliferated, reinforced by the dynamics of western expansion along the unfolding American frontier. Industrialization, immigration, home missions, and the growth of the Black church added to the diversity and richness of Protestant Christianity, as did the explosion of reform movements and the religious fervor of the Second Great Awakening. Yet abolitionism and the sectional crisis of the 1840s and 1850s further segmented religious organizations into Northern and Southern divisions, until in the Civil War Protestant theology and piety coursed through both Union and Confederate societies.