By Sam W. Haynes
University of Texas at Arlington
The 1840s were years of extraordinary territorial growth for the united States. During a four year period, the national domain increased by 1.2 million square miles, a gain of more than sixty percent. So rapid and dramatic was the process of territorial expansion, that it came to be seen as an inexorable process, prompting many Americans to insist that their nation had a "manifest destiny" to dominate the continent.
Yet, the expansionist agenda was never a clearly defined movement, or one that enjoyed broad, bipartisan support. Whig party leaders vigorously opposed territorial growth, and even expansionist Democrats argued about how much new land should be acquired, and by what means. Some supporters of Manifest Destiny favored rapid expansion and bold pursuit of American territorial claims, even at the risk of war with other nations. Others, no less committed to the long-term goal of an American empire, opposed to the use of force to achieve these ends, believing that contiguous land would voluntarily join the Union in order to obtain the benefits of republican rule. In an often-used metaphor of the day, these regions would ripen like fruit and fall into the lap of the United States. Thus the champions of Manifest Destiny were at best a motley collection of interest groups, motivated by a number of divergent objectives, and articulating a broad range of uniquely American concerns.
Several factors help to explain why the United States embarked upon an aggressive program of expansion during this period. In the early decades of the nineteenth century, many Americans had dismissed as fanciful the idea of a transcontinental republic, convinced that the bonds of Union would weaken as the nation grew larger. But such vast distances were quickly being conquered by technological innovations. By the 1840s, steamboats had turned America’s waterways in busy commercial thoroughfares, while a network of railroads integrated eastern markets with towns and cities on the western slope of the Appalachians. The telegraph, first used in 1844, ushered in a modern age of long distance communication. An American dominion stretching from the Atlantic to the Pacific now seemed within reach.
Although the United States had no shortage of unoccupied lands, expansionists argued that the republic must continue to grow in order to survive. Echoing the political philosophy of Thomas Jefferson, they viewed an abundance of land as the mainstay of a prosperous republic, and warned against the concentration of political and economic power. Troubled by creeping urbanization and a rising tide of immigrants from Germany and Ireland, expansionists viewed Manifest Destiny as a means to obtain a new, long-term lease on the Jeffersonian ideal. Far from weakening the republic, they argued, territorial growth would actually serve to strengthen it, providing unlimited economic opportunities for future generations.
Expansionists were also motivated by more immediate, practical considerations. Southerners anxious to enlarge the slave empire were among the most ardent champions of the crusade for more territory. New slave states would enhance the South’s political power in Washington and, equally important, serve as an outlet for its growing slave population. For American commercial interests, expansion offered greater access to lucrative foreign markets. Washington policy-makers, anxious to compete with Great Britain for the Asia trade, had long been convinced of the strategic and commercial advantages of San Francisco and other ports on the Pacific coastline of Mexican-owned California. The disastrous Panic of 1837, which had resulted in huge surpluses and depressed prices for American farm products, also focused attention on the need to develop new foreign markets.
Most important of all, perhaps, was the growing sense of anxiety which Americans felt toward Great Britain. Americans had always been suspicious of British activities in the western hemisphere, but inevitably this fear had grown as the United States began to define its strategic and economic interests in terms that extended beyond its own borders. Great Britain’s claim to the Pacific Northwest and its close relationship with Mexico were matters of great concern to American interests, which viewed Great Britain as the United States’ only rival for control of the Pacific coastline. Fearful of being "hemmed in" by Great Britain, Democratic leaders saw Her Majesty’s government poised to block American territorial ambitions at every turn. In addition, southern slaveowners were particularly apprehensive of Great Britain, which had abolished slavery in its West Indies colonial possessions in 1833. In 1843, southern statesmen alleged, on the basis of little evidence, that Great Britain was actively engaged in a plot to abolish slavery throughout North America. These rumors provoked a frenzied outcry in the South, which called for the immediate annexation of the Texas Republic in order to secure the interests of the planter class in the cotton-growing regions of North America.
This fear of British designs, real and imagined, changed the face of Manifest Destiny, converting many advocates of gradual expansion into apostles of a new, more militant brand of imperialism. By the mid-1840s, with Great Britain rumored to be plotting with Mexico to block Washington’s efforts to annex the Texas Republic and scheming to acquire California, U.S. expansionism took on a greater sense of urgency. Elected on a pro-expansion platform in 1844, Democrat James K. Polk moved quickly to annex Texas as the twenty-eighth state. Polk also threatened to disregard long-standing British claims to Oregon, convinced that he only way to deal with "John Bull is to look him straight in the eye." Polk’s defiant brinkmanship would ultimately lead to a compromise with Her Majesty’s government over the Oregon territory, while precipitating a war with Mexico, whose government, Polk incorrectly believed, was acting in concert with Great Britain to thwart U.S. territorial ambitions. Although Polk insisted that the United States was not waging a war of conquest, critics accused the president of manufacturing a war to seize California and New Mexico. In the months following the war, Polk also considered extending U.S. sovereignty over the Yucatan peninsula and Cuba, two regions which he believed were vulnerable to encroachments from the British. These initiatives received little support in Congress, however, and were abandoned shortly before Polk stepped down from office.
In the 1850s, having established itself as a transcontinental empire, the United States ceased to regard British activities in the western hemisphere with alarm. Preoccupied with the increasingly bitter sectional conflict over slavery, many Americans rejected Manifest Destiny. Although southern extremists would sponsor filibuster expeditions into Latin America with the objective of gaining new lands to extend the slave empire, the expansionist movement faded from the national agenda in the years prior to the outbreak of the Civil War.