In the earliest years of the Republic, both George Washington and Thomas Jefferson called upon Americans to actively seek to preserve their nation's unique position of aloofness from the world's ills. In his Farewell Address of 1796, Washington warned against "permanent alliances," while Jefferson, in his First Inaugural Address (March 1801), advised that Americans should avoid "entangling alliances." Such pronouncements laid the foundations for a foreign policy characterized by high levels of unilateralism and so-called isolationism. Jefferson nevertheless presided over the first major expansion of the United States with the Louisiana Purchase (1803) and contributed to the notion that a republic needed to grow in order to remain healthy with his view of the United States as an "empire for liberty."
President James Monroe further emphasized the difference between American and European intentions in foreign affairs on 2 December 1823, in what became known as the Monroe Doctrine. Monroe declared the Western Hemisphere closed to European colonization, warned against European interference in the affairs of the Americas, and signaled the intention of the United States to be the region's dominant power. Although the Monroe Doctrine was based largely on strategic interest, it was couched in terms consistent with the belief in exceptionalism. Monroe stressed that the United States held nothing but goodwill toward the world's nations and emphasized that the U.S. policy of noninterference in European affairs marked it apart from the imperialistic nations of the Old World. As Monroe's Secretary of State John Quincy Adams had stated famously on 4 July 1821, the United States "goes not abroad, in search of monsters to destroy." Adams was expressing another crucial element of the conviction that the United States would avoid repeating the faults of the Old World. The United States is deemed exceptional because it is believed to be incapable of seeking dominion over others in its own self-interest. It would, then, avoid the temptations that had caused all great nations to seek expansion of their power by conquering and subjugating other peoples. If the United States did intervene abroad, it would be for the good of others, in the name of higher principles. As Adams insisted, America's "glory is not dominion, but liberty."
This belief in the basic benevolence of all U.S. actions abroad was further emphasized by President James K. Polk in his reassertion of the Monroe Doctrine on 2 December 1845. He emphasized that the United States had taken upon itself the responsibility not only for its own freedom and security but also for that of all the nations in the Western Hemisphere. According to Polk, the United States did not pursue wars of conquest, but it would do whatever necessary to defend the independence of the Americas. It would not tolerate the interference of a self-interested imperial power in its region yet, paradoxically, it considered its own interference in a neighbor's affairs as being to the benefit of the neighbor. Such a policy was, of course, the declaration of an ambitious state seeking hemispheric dominance. But subsumed within the doctrine was an assumption that American intervention would not amount to self-interested foreign interference. According to the tradition of exceptionalism, the United States is incapable of doing ill to others, and therefore the nature of its interference in the Americas would be inherently more benign than that of any other foreign power. Polk stretched the credibility of such claims with the war against Mexico in 1846. In his public rhetoric, he justified his ambitions for the acquisition of new land and the provocative nature of his actions toward Mexico by couching the conflict in terms that were consistent with his pronouncements on the exceptional nature of U.S. foreign relations, and cast the United States as the innocent party. Indeed, a new phrase had entered the American vocabulary that helped explain westward expansion as an integral part of American exceptionalism.