This dissertation explores the intersection of the New Deal and the war on crime in the 1930s and 1940s, and argues that their interaction drove state-building in three major ways. First was the expansion and modernization of American law enforcement and criminal justice. Second was the legitimation of national political authority, which had been unstable since Reconstruction. This legitimation relied on a new war on crime coalition built by the Roosevelt administration. Third was the transformation of American government, particularly in the structure of American federalism, which in turn transformed American liberalism as both a political ethos and a political program. The chapters narrate the predicament for American law and order from the late-nineteenth century through World War II, and along the way describe the New Deal developments in criminal law, the FBI, criminological thought, drug control, constitutional interpretation, and security-state policy.