ROOTED IN CONFLICTING conceptions of the federal Union almost as old as the government itself, the American Civil War was a constitutional crisis of the most profound sort. After secession disrupted the Union, the purpose of the war in the most fundamental sense became the determination of how American government would be constituted. The federal republic of 1787 might be restored, a consolidated, sovereign national government might evolve, or, at the opposite extreme, two systems of federated states might be created. The crisis involved more than the question of political organization, however, because the force and violence of organized warfare militated against, if they did not inherently contradict, the conduct of politics by the rules and principles of constitutionalism. The Civil War tested not only America's unique system of federalism but also its distinctive method of constitutional politics.
The twofold constitutional crisis that occurred during the Civil War had its origin in the controversy over slavery. The first aspect of the crisis—the problem of continental political organization—took shape in the 1840s when westward expansion required Americans to define anew the relationship between slavery and the republic. Southerners, proposing the theory of state sovereignty, argued that the slave states had exclusive power to decide all questions of law and policy concerning slavery in the territories. After events in Kansas during the 1850s taught southerners that popular sovereignty would not support their interests, the South demanded outright federal