During the first decades of the nineteenth century, the United States established itself as a dominant power in the Western Hemisphere. This was no small accomplishment for a young nation with fragile unity and a minuscule military. Presidents Thomas Jefferson, James Madison, and James Monroe exploited Europe's preoccupation with the Napoleonic wars and the relative weakness of potential rivals in North America. They constructed what Jefferson called an "empire of liberty" that combined force and commerce with a sincere commitment to enlightened government in "savage" lands.
America's self-confidence in the righteousness of its revolutionary model motivated many of the bloodiest massacres and dispossessions of native communities during this period. For Jefferson in particular, those who resisted democratic government and economic penetration threatened the American cause. Resistance justified temporary repression and, when necessary, brutalization. Nonwhite races received the most violent treatment. They appeared "immature" and "unprepared" for the blessings of liberty. Americans defined themselves as paternalists, caring for blacks and Indians until these groups were ready (if ever) for democratic self-governance. In this curious way, American sincerity about revolutionary change inspired more complete domination over nonwhite communities than that frequently practiced by other, less ideologically imbued imperial powers.
The American acquisition of the Louisiana Territory from France in 1803 doubled the size of the country. It allowed Jefferson to make his "empire of liberty" a reality. With full control of the Mississippi River, the United States could conduct commerce along the north-south axis of the continent free from European interference. Exploring, apportioning, and eventually settling the vast western territories, the United States would now "civilize" its surroundings, as envisioned in Franklin's Albany Plan of 1754. Foreign powers and Indian communities had, in American eyes, prohibited the spread of liberty and enterprise. By sponsoring a famous cross-continental "journey of discovery" directed from 1804 to 1806 by Meriwether Lewis and William Clark, Jefferson provided a foundation for altering the West with the creation of national markets, state governments, and, very soon, railroads. The transformation of the territories acquired with the Louisiana Purchase involved the rapid and forceful extension of America's Revolution.
During this same period, residents of French, Spanish, and Portuguese colonies in the Western Hemisphere revolted against European authority. While Americans remained wary of revolutions directed by nonwhite peoples, the U.S. government supported independence in Haiti, Mexico, Colombia, Brazil, and other former imperial possessions. Nonwhite revolutionaries, like Toussaint Louverture in Haiti, received aid, goodwill, and, most importantly, inspiration from Americans.
Fearful that the European powers, including Russia, would attempt to repress the Latin American revolutions, President James Monroe and his secretary of state, John Quincy Adams, worked to exclude this possibility. On 2 December 1823 the president announced what later became known as the Monroe Doctrine in his annual message to Congress. It explicitly prohibited "future colonization by any European powers" in the Western Hemisphere. The doctrine asserted the predominance of U.S. interests. The president and his secretary of state believed that the security of American borders, trading lanes, and revolutionary principles required freedom from Old World intervention.
Throughout the rest of the nineteenth century, the British navy enforced the Monroe Doctrine in order to weaken London's European rivals; American words and British seapower sheltered revolutionaries from their previous imperial oppressors. At the same time, the United States stepped into the place of the colonial empires, assuring that political and economic change followed its model. Americans intervened south of their border to support revolutions that promised democratic governance and free trade. They repressed revolutions that entailed extreme violence, limitations on commerce, and challenges to U.S. regional domination. As in their policies toward France during the late eighteenth century, Americans welcomed rapid change throughout the Western Hemisphere, but only on their own terms.