This book situates the origins of American political science in relation to the transatlantic history of liberalism. In a corrective to earlier accounts, it argues that, as political science took shape in the nineteenth century American academy, it did more than express a pre-existing American liberalism. The pioneers of American political science participated in transatlantic networks of intellectual and political elites that connected them directly to the vicissitudes of liberalism in Europe. The book shows how these figures adapted multiple contemporary European liberal arguments to speak to particular challenges of mass democratic politics and large-scale industry as they developed in America. Political science's pioneers in the American academy were thus active agents of the Americanization of liberalism. When political science first secured a niche in the American academy during the antebellum era, it advanced a democratized classical liberal political vision overlapping with the contemporary European liberalism of Tocqueville and John Stuart Mill. As political science expanded during the dramatic growth of university ideals and institutions in the Gilded Age, divergence within its liberalism came to the fore in the area of political economy. In the late-nineteenth century, this divergence was fleshed out into two alternative liberal political visions-progressive liberal and disenchanted classical liberal-with different analyses of democracy and the administrative state. During the early twentieth-century, both visions found expression among early presidents of the new American Political Science Association, and subsequently, within contests over the meaning of 'liberalism' as this term acquired salience in American political discourse. In sum, this book showcases how the history of American political science offers a venue in which we see how a distinct current of mid-nineteenth-century European liberalism was divergently transformed into alternative twentieth-century American liberalisms.