The phrase 'Young America' connoted territorial and commercial expansion in the antebellum United States. During the years leading up to the Civil War, it permeated various parts of the Democratic party, producing new perspectives in the realms of economics, foreign policy, and constitutionalism. Led by figures such as Senator Stephen A. Douglas of Illinois and editor John L. O'Sullivan of New York, Young America Democrats gained power during the late 1840s and early 1850s. They challenged a variety of orthodox Jacksonian assumptions, influencing both the nation's foreign policy and its domestic politics. This is the first book to offer an exclusively political history of Young America's impact on the Democratic Party, complementing existing studies of the literary and cultural dimensions of this group. This close look at the Young America Democracy sheds light on the political realignments of the 1850s and the coming of the Civil War, in addition to showcasing the origins of America's longest existing political party.