The United States dominates the world as no state has. It emerged from the Cold War as the world's only superpower and no geopolitical or ideological contenders are in view. Its dynamic bundle of oversized capacities, interests, and ideals together constitute an "American project" with an unprecedented global reach. For better or worse, states today must operate in, come to terms with, or work around this protean order. This book of essays explores the theoretical, historical, and foreign policy implications of American power and postwar order. Written over the last decade and a half, these scholarly and policy essays form a sort of "intellectual arc" of inquiry. The first part of the book focuses on the origins and foundational logic of America's postwar order-building project - advancing ideas about "liberal hegemony" and "constitutional order." The second part reflects on its evolving character and fate in the aftermath of the Cold War, the rise of unipolarity, and the post-911 threat of global terrorism. In this unique study of a superpower, Ikenberry argues that though the American world order is now in upheaval, in the end, the United States still has powerful incentive to sponsor and operate within a liberal rules-based system.