Throughout the nineteenth century one notable American activity—continental expansion—regularly threatened to revive the power problem and to exacerbate disagreements over the relative merits of force and suasion in foreign affairs. Time and again Americans took advantage of opportunities for territorial expansion, but few such opportunities were without opposition from the established powers of the day. The United States had to face British opposition in the Old Northwest until the signing of Jay's Treaty in 1794. Within a generation there were the further complications of the Oregon dispute. Despite the jingoist cry of "Fifty-four forty or fight," the Oregon question was settled peacefully, but there remained contentions over the Canadian-American boundary, including Alaska, until 1903. French resistance to American expansion seemed to disappear with the Louisiana Purchase of 1803, but it reappeared in the diplomacy and maneuvering surrounding the annexation of Texas, the war with Mexico, and during the Civil War in the illfated imperium of Maximilian in Mexico. Spanish-American antagonism over expansion marked the era of the 1790s and of separatism in the early American Southwest, flared in connection with the disputed boundaries and the American annexations of East Florida and West Florida as well as over use of the Mississippi River, and culminated in contests for predominance in Cuba and the Philippines in the Spanish-American War (1898). The United States even managed to come into conflict with Russia in the matter of the Oregon boundary, which provided occasion for some of John Quincy Adams's most pointed démarches.
Expansionism also affected those without sufficient power to resist or negotiate its progress across the continent. For four centuries expansion was the central theme of European-Indian relations. Much of the devastation of the Indian peoples in colonial America can be attributed to disease. But their fate was also the result of how white Americans used their power in dealing with Indians. A succession of treaties attempted to reconcile the traditional cultural norms of huntinggathering, often nomadic, communal peoples with the demands of an expanding agrarian, capitalist culture driven by an unprecedented immigration and population explosion. Twenty-five years before the American Revolution, Benjamin Franklin used demographic projections to prove the need for new lands in the west to support a population that doubled every twenty years. He also pointed out that such expansion would mean war with the Indians and their French allies—a price Franklin and others before and after him were willing to pay.
Other Americans wrestled with the "Indian problem." Thomas Jefferson considered these "noble savages" possible candidates for assimilation. Andrew Jackson rationalized removal of the so-called Civilized Tribes of the Southeast to Indian Territory beyond the Mississippi as a version of protective custody. The reservation system continued this "Great White Father" paternalism. On both sides of the debate over Indian policy, what were termed humanitarians and exterminationists shared social Darwinism ideas of white racial and cultural superiority and faith in the inevitably of progress in the form of the economic development of the American frontier. The West, or frontier, was both a powerful myth in the American mind and in reality a colonial area to be exploited for its resources by the more developed East and investors from abroad. Indians, buffalo, the environment itself had to give way to this economic imperative wrapped in the myth of progress, prosperity, and "manifest destiny."
Often Americans regarded continental expansion as a matter of destiny and strength, the strength of righteousness. Because the United States was a progressive, moral, humane country, its extension to the Pacific Ocean was foreordained, proper, and inexorable. In contrast to the repressive Old World empires, theirs was an "empire of liberty." The end justified the means in this case, and most Americans believed that in the grand process of expansion, force was allowable and probably necessary. It was likewise necessary to counter the attempts of Old World governments to subdue other territories in the New World and reintroduce autocratic government and Machiavellian diplomacy into the hemisphere.
To a certain extent the enthusiastic expansion and protection of American interests by John Quincy Adams, James Monroe, James Polk, and the signers of the Ostend Manifesto (1854), which set forth American designs on the annexation of Cuba, were counterbalanced by the hesitations and objections of other prominent Americans. Some people doubted the wisdom and propriety of each expansion of national domain, especially beginning with the Louisiana Purchase. There were dissenters in each instance of armed conflict—for example, Henry David Thoreau's civil disobedience and jailing during the Mexican War. Expansionist secretaries of state such as William Seward were succeeded by more restrained and prudent men such as Hamilton Fish, who rejected some of the grand imperial designs toward the Caribbean and Mexico that his predecessor had elaborated. Despite internal disagreements and external power problems, by the end of the nineteenth century the process of continental expansion had resulted in an American "imperial democracy" that stretched from Atlantic to Pacific and included Puerto Rico, Hawaii, Guam, and the Philippines. That continental expanse and newly acquired overseas empire was bolstered by an economic power that rivaled and in many cases surpassed that of the Old World colonial empires. By virtually any measurement the United States had become a world power.