Americans have long debated whether the Civil War was a defeat for states’ rights and whether it changed the balance of power between state and national governments. For generations, the answer seemed clear. Whether in praise or complaint, Americans largely acknowledged that the Civil War marked a growth spurt in the history of the American state. The Civil War indeed expanded the size of the federal military dramatically, turned Washington DC into a massive contractor funding many expanding industries, opened the door for federal land redistribution to fund universities and railroads, and seemingly transformed the constitutional balance between the general and state governments in a series of constitutional amendments, particularly the Fourteenth. Through a combination of temporary expansion, constitutional transformation, and privatization, the US government grew significantly during the war. The defeat of the Confederate states thus seemed to be a defeat for states’ rights more generally. Yet historians are far less confident than they used to be that the Civil War actually transformed the federal government, much less the more abstract notion of the “American state.” Rather than a forerunner of twentieth-century Progressivism or New Deal governance, the US Civil War may in fact have been a distinct and temporary moment in American governance, a period of momentary but not sustained expansion.