In the mid-nineteenth century, newspaper editor John O'Sullivan coined the term 'manifest destiny' to describe the belief that God intended for the United States to occupy North America from Atlantic to Pacific. 


  • Manifest Destiny was the idea that white Americans were divinely ordained to settle the entire continent of North America.
  • The ideology of Manifest Destiny inspired a variety of measures designed to remove or destroy the native population.
  • US President James K. Polk (1845-1849) is the leader most associated with Manifest Destiny.
  • Manifest Destiny inflamed sectional tensions over slavery, which ultimately led to the Civil War.

From sea to shining sea

In 1845, newspaper editor John O’Sullivan coined the term “manifest destiny” to describe the ideology of continental expansionism.
Though the term was new, the ideas underlying it were much older, dating back to the first colonial contact between Europeans and Native Americans. The ideology that became known as “manifest destiny” included a belief in the inherent superiority of white European-Americans, as well as the conviction that whites were destined by God to conquer the territories of North America, from sea to shining sea.
Manifest Destiny justified extreme measures to clear the native population from the land, including forced removal and violent extermination. For proponents of Manifest Destiny, the American Indians were mere impediments to the forward march of racial and technological progress, and they advocated pursuing a policy of Indian Removal.1^1
Painting: John Gast, American Progress, 1872. The artist depicts Columbia, an allegorical figure of America, bring elements of 'civilization' west. As railroads, settlers, and telegraph wires come west, American Indians and bison scatter before them.
John Gast, American Progress, 1872. The artist depicts Columbia, an allegorical figure of America, bring elements of 'civilization' west. As railroads, settlers, and telegraph wires come west, American Indians and bison scatter before them. Image courtesy Wikimedia Commons.

James K. Polk and Manifest Destiny

US President James Knox Polk, who served one term in office, from 1845 to 1849, is the leader most associated with the ideology of Manifest Destiny. Polk was a Democrat from Tennessee who had served as Speaker of the House of Representatives and Governor of Tennessee before becoming president. As president, he led the United States to victory over Mexico in the Mexican-American War of 1848, which culminated in the transfer of a vast new territory, comprising almost the whole of the modern-day Southwest, from Mexico to the United States.2^2
Polk also resolved the boundary dispute with Great Britain over the Oregon Territory, which had been jointly occupied since 1818. Though he had campaigned on the slogan “54-40 or fight!”, which referred to the latitude (in degrees and minutes) of the Oregon Territory up to the southern border of Russian Alaska, he ultimately negotiated the Oregon Treaty of 1846 with Britain, which accepted a division of the territory at the 49th parallel. The territory acquired by the United States under the provisions of the treaty include the states of Idaho, Oregon, and Washington, as well as parts of Montana and Wyoming.
Map of Oregon territory, showing the present day states of Washington, Oregon, Idaho, and parts of Montana and Wyoming.
Map of the Oregon Territory. The United States and Great Britain disputed the boundary line, shown here at the final boundary of the 49th parallel. Map courtesy Wikimedia Commons.

Manifest Destiny and the road to the Civil War

The conquest of new territories on the North American continent inflamed sectional tensions over slavery. The precarious balance of power in Congress between the slaveholding South and the abolitionist North led to a series of compromises. The Wilmot Proviso, for instance, was an amendment asserting that the Mexican-American War had not been fought for the purpose of expanding slavery, and stipulated that slavery would never exist in the territories acquired from Mexico in the war. For obvious reasons, the slaveholding South opposed the proviso, and the struggle over the issue of slavery in the newly acquired territories was one of the major signposts on the road to the Civil War.3^3

What do you think?

Why do you think Polk went to war with Mexico but negotiated with Great Britain?
In your view, what was the most significant component of the ideology of Manifest Destiny?
What sorts of policies were justified in the name of Manifest Destiny?
What were the most consequential outcomes of the ideology of Manifest Destiny?
Article written by Dr. Michelle Getchell. This article is licensed under a CC-BY-NC-SA 4.0 license.
  1. For more on the history of Manifest Destiny and the Native American Indians, see Robert J. Miller, Native America, Discovered and Conquered: Thomas Jefferson, Lewis and Clark, and Manifest Destiny (Lincoln: University of Nebraska Press, 2008).
  2. For more on the Mexican-American War, see Robert W. Merry, A Country of Vast Designs: James K. Polk, the Mexican War, and the Conquest of the American Continent (New York: Simon and Schuster, 2009).
  3. See Steven E. Woodworth, Manifest Destinies: America’s Westward Expansion and the Road to the Civil War (New York: Random House, 2010).