Chapter 3 re-examines the “ascent” of the United States within the 19th century’s Eurocentric international order, retracing its special path from a fledgling and vulnerable republic to the status of an exceptional and exceptionalist world power. It focuses on the evolution of American ideas and ideologies in the sphere of international affairs, the rise of distinctive forms of US imperialism and unilateralism, and the emergence of core maxims of US international conduct such as those embodied in the ever more expansively defined Monroe Doctrine and the Open Door Doctrine. It then casts new light on ephemeral aspirations to establish a modern Atlantic order of empires – led by the United States and the British Empire – that were pursued after the Spanish-American war of 1898 and in the era of Theodore Roosevelt.