What Is Manifest Destiny?
Manifest Destiny was the belief that U.S. expansion west to the Pacific Ocean and south to part of Mexico was inescapable, ethical, necessary, and even divinely ordained. It was a belief that arose from contemporary notions behind the global phenomenon of imperialism. The term was first used in 1845 by an editor of a Democratic Party journal in which he argued for the annexing of Texas. It received little attention. But he used the term a second time in a New York City newspaper discussing the dispute between the United States and Great Britain over the Northwest Oregon territory. It was then that expansionist Democrats picked up the term. It became a slogan, a rallying cry, and a rationale for foreign policy in 1845–46.
The concept of Manifest Destiny, however, was not new. European expansion into North and South America was also driven by the colonists' "divine" needs to discover and conquer new lands. It was fundamental to both the explorers' and early colonists' thinking. From the early discoveries, Europeans sought to claim additional land as settlers moved ever westward and into the Southwest.
In 1844 Democrat James Polk won the presidential election. In his campaign he openly demanded expansion of the United States, including the annexation of Texas. Since 1836 it had been independent of Mexico, and many thought it should be a part of the United States. Polk also campaigned for the whole territory of Oregon to be part of the United States rather than a territory shared jointly with British Canada. In particular the boundary line was in dispute. Polk's campaign slogan was "Fifty-four forty or fight," referring to the latitude 54°40′ for the boundary line he sought between the British territory of Canada and the United States. The line lay much farther north than the 49th parallel, at the southern border of the Russian territory of Alaska.
Period of Rapid Expansion
During Polk's presidency, the United States gained a sweeping stretch of territory from a war with Mexico. At the war's conclusion in 1848, the United States acquired the Southwest and California. Earlier, with the Oregon Treaty of June 1846, the boundary line between Great Britain/Canada and the United States was set at the 49th parallel. Despite Polk's bold pledge to fight for the latitude 54°40′, the Mexican-American War had distracted Washington leadership, and the Senate approved the treaty establishing the boundary line farther south.The period of rapid expansion closed with the treaty ending the Mexican-American War in 1848. The United States now extended west to the Pacific Ocean, northwest to the 49th parallel, and south to the Rio Grande—all this in less than 100 years since the American Revolution. To many Americans this was a considerable accomplishment and further proof of divine approval for the United States to thrive and prosper. A final parcel of land less than 30,000 miles square was acquired from Mexico in the Gadsden Purchase (1853–54). That land would later become parts of New Mexico and Arizona.