The nineteenth century witnessed the transformation of the United States from an insecure association of erstwhile colonies to a continental empire with a global reach. Though forged in a struggle for independence from the British Empire, the United States became a formidable empire in its own right. Historians have long recognized the significance of this transition for the United States and the world, but they have given different meanings to it over time and place. In contrast to critics in Latin America, the Caribbean, and other loci of anti-imperialist sentiment, most US scholars writing before the Vietnam War and contemporaneous civil rights movement regarded the “rise” of the United States as something to be celebrated. America’s republican institutions, in this telling, challenged the oppressive monarchical order of the Old World, while white settlers’ march across the North American “frontier” gave birth to an exceptionally democratic national character.