Manifest Destiny

Expansionism and Imperialism

By Thomas Hietala

The United States experienced its most rapid territorial growth during the mid-1840s. The nation annexed Texas in 1845, acquired Oregon south of 49° north latitude in a treaty with Great Britain in 1846, and conquered and held California and New Mexico during the U.S.-Mexican War. The nation also obtained vast cessions from Native American tribes, which were relocated to remote and unwanted regions, a process begun in the seventeenth century.

Journalist John L. O'Sullivan attributed this remarkable expansion to "Manifest Destiny," a label scholars still use to describe the decade. But O'Sullivan did not formulate a clear or coherent definition of Manifest Destiny. In 1845 he interpreted the phrase to mean that the United States was predestined to control the entire continent because God wanted it that way. But O'Sullivan soon abandoned his original doctrine. In 1846 he supported a war of conquest against Mexico and in 1848 he urged that Cuba and Yucatan be made a part of the United States, by purchase or by force. O'Sullivan coined a catchy phrase for the expansionism of the 1840s, but his concept does not explain the motives, means, and goals behind aggrandizement.

The historical evidence on this topic is abundant, contradictory, and often misleading. Presidents John Tyler and James K. Polk, their advisers, and their partisans in Congress supported territorial acquisitions, but their reasons for doing so varied widely. Although they sometimes invoked the idea of Manifest Destiny to justify expansion, they primarily sought land, markets, and ports for materialistic, not idealistic, ends. Like other empires, the United States sought power, wealth, security, and mobility for a fast growing population. Scholars generally agree that the United States rivaled other modern empires in the rapidity and degree of its enlargement. They differ, however, on the extent of similarity between the United States and traditional imperial powers such as Great Britain, France, Spain, and Russia. The United States, like its rivals, obtained territory by means both fair and foul. The chief difference, however, was that U.S. leaders in the 1840s eschewed colonialism and militarism. They intended to transform acquisitions into states equal in status to those already in the Union.

When O'Sullivan introduced Manifest Destiny in 1845, he predicted his country would acquire California in the same way it had just acquired Texas. Pioneers would venture to California, eclipse Mexicans and Native Americans, win independence, and then seek admission to the Union. Before the U.S.-Mexican War, Thomas Ritchie, summoned to Washington, D.C., by President James K. Polk to edit a newspaper favorable to his administration and policies, stressed the purity of previous cessions. "Our government is not extended by the sword," he wrote. "By its own merits it extends itself." Polk and his cabinet, however, lacked the patience to rely on the nation's "own merits," its pioneers, or providence to obtain California. Instead, they ordered Gen. Zachary Taylor and his troops into disputed territory between the Nueces River and the Rio Grande.

Both the United States and Mexico miscalculated in 1846. Contemptuous of Mexico's government and army, Polk and his advisers tried to intimidate Mexican officials into ceding California and other provinces to the United States to pay outstanding claims owed to U.S. citizens. Mexico, for its part, erred in assessing its northern neighbor's ability to raise and equip an effective military. Moreover, Mexican leaders miscalculated their nation's capacity to rally the church, the army, and the people to repel the invaders. Still stung by the loss of Texas, Mexican leaders vowed to resist further dismemberment. But in trying to avenge a previous defeat, they lost California and New Mexico.
Some scholars contend that Polk purposely goaded Mexico into war. Though he acted provocatively, he apparently hoped to realize his goals without war. The bloodshed in 1846 signified failure, not success, in his strategy. Polk deployed the army to gain territory, a move that alarmed the Whigs. Two months into the war, U.S. representative George Ashmun, from Massachusetts, rebuked the president. "It is no longer pretended that our purpose is to repel invasion," he protested, "The mask is off; the veil is lifted; and we see. . . invasion, conquest, and colonization, emblazoned upon our banners." Ashmun and other Whigs could not reconcile Polk's course with ideals of innocence and exceptionalism. Democrats, however, replied that Polk was beyond reproach. When the war ended, Sen. Sidney Breese of Illinois argued that his country's historic commitment to peace and national honor had been maintained. "We have never, sir, since the birth of our nation, given occasion for war, not even with the barbarous tribes upon our borders," he insisted. "It is our pride. . . that our whole history may be explored, and no single act of national injustice can be found upon its page-no blot of that kind upon our national escutcheon."

Politicians, editors, soldiers, and citizens, wanted new terrirory for various reasons. In the case of Texas, the Tyler administration sought to prevent the abolition of slavery there, control a potential rival in cotton production, provide a haven for masters and their slaves, thwart Great Britain from keeping Texas independent, and comply with the wishes of most Texians to join the United States. In the Oregon dispute, Democrats hoped to dominate Asian commerce, provide land for future pioneers, and safeguard citizens already settled there. The war with Mexico and the strategy of conquest revealed a desire to secure a border at the Rio Grande, satisfy claims against Mexico, and acquire California to monopolize trade with Asia. Democrats wanted to supply abundant land to the nation's poor and to future immigrants. To attain this laudable goal, however, they relied on bribery, bullying, and warfare to wrest land from Native Americans and Mexicans. Often idealistic, they were also racist and materialistic.

Without opinion polls and single-issue elections from this era, scholars have limited data for measuring the popularity of expansionism. Each state was different, and attitudes changed with time. The war, for example, aroused far greater enthusiasm in mid-1846 than it did one year later. Polk won in 1844 on a strident party platform demanding the "reannexation" of Texas and the "reoccupation" of Oregon. But his party lost clout in Congress after the war began and lost the presidency in 1848. No subsequent decade matched the expansion of the 1840s, but leaders and private groups continued to seek more land from Native Americans, Central American countries, and European governments. Some adventurers resorted to filibustering expeditions to Cuba and Nicaragua. Among those who supported these private armies was John L. O'Sullivan. With the national government deadlocked over slavery and its extension after the U.S.-Mexican War, adventurers who sought new slave territories, commercial opportunities, or personal glory planned, financed, and occasionally conducted private invasions and occupations of Latin American nations and colonies. These filibusters generally hailed from the South and the best known among them was William Walker, whose execution in Honduras in 1860 marked the inglorious end of these unofficial efforts to extend Southern slavery below the Rio Grande.