Marc Egnal's Clash of Extremes challenges the orthodoxy that the Civil War began for moral reasons. Egnal contends that more than any other concern, the evolution of the Northern and Southern economies explains the sectional clash. Drawing on a wealth of primary and secondary sources, Clash of Extremes shows that between 1820 and 1850, patterns of trade and production drew the sections together. For example, the Mississippi River provided a strong north-south axis while planters earned high profits on fertile soils. Those ties allowed sectional leaders to broker a series of compromises. After...