Manifest Destiny was the belief held by many Americans in the 19th century that the United States was destined by God to expand its territory across the entire North American continent, from the Atlantic Ocean to the Pacific Ocean. This idea shaped the country’s politics, foreign policy, and westward expansion for much of the 1800s. It was also used to justify the displacement of Native Americans and the conquest of land from other nations.
What Was Manifest Destiny?
Manifest Destiny was not a law or an official government policy. Rather, it was a widely shared idea that American expansion westward was both inevitable and right. Many Americans believed that their democratic values, their Christian faith, and their way of life were superior to those of other peoples, and that it was their duty to spread those values across the continent. In fact, the idea was deeply tied to racial prejudice, as those who promoted it most strongly tended to believe that white, Protestant Americans were more suited to settle and govern the land than the Native peoples, Mexicans, or other groups already living there.
The phrase itself was first used in print in July of 1845 by John L. O’Sullivan, the editor of a publication called the United States Magazine and Democratic Review. O’Sullivan wrote in favor of the United States annexing Texas, arguing that other nations should not interfere with what he described as America’s right to spread across the continent. He expanded on the idea later that year in his newspaper, the New York Morning News, where he argued that the United States had the right “to overspread and to possess the whole of the continent which Providence has given us.” For many Americans, those words captured something they had long believed without having a name for it.
Background – Roots of American Expansion
The belief in America’s right to expand westward did not begin with O’Sullivan. Long before the phrase was coined, American settlers and politicians had been pushing the boundaries of the country further and further west. This drive had its roots in the earliest years of European colonization, when settlers immediately looked inland and began pushing into new territory.
After the American Revolution, the young United States began expanding quickly. In 1803, President Thomas Jefferson completed the Louisiana Purchase, buying approximately 828,000 square miles (2,144,500 square km) of territory from France for roughly $15 million. This deal nearly doubled the size of the country and stretched American claims all the way to the Rocky Mountains. Jefferson then sent explorers Meriwether Lewis and William Clark to chart the new territory, fueling even greater interest in the lands to the west.
In 1819, the Adams-Onis Treaty with Spain gave the United States control of Florida and also established an American claim to the Pacific Northwest, as Spain gave up its rights to the Oregon Country. By the 1820s, American settlers were steadily moving westward, and the idea that the entire continent was meant to be American was becoming more and more common.
The Role of President James K. Polk
No president was more closely associated with Manifest Destiny than James K. Polk, who won the presidential election of 1844 on a platform built largely around westward expansion. Polk and his supporters had their eyes on Texas, Oregon, and California. His election signaled that a large portion of the American public shared his expansionist goals.
Polk was a firm believer that it was America’s right and duty to stretch its territory to the Pacific coast. During his time in office from 1845 to 1849, the United States added more territory than at any other time in its history outside of the Louisiana Purchase. For this reason, Polk is often seen as the president who most fully put the idea of Manifest Destiny into practice.
Texas Annexation
One of the first major steps in the era of Manifest Destiny was the annexation of Texas. Americans had been settling in the region for decades, and in 1836 Texas declared its independence from Mexico following the Texas Revolution. For several years, Texas existed as an independent republic, but many Texans and Americans favored bringing the new republic into the United States.
The annexation of Texas was politically complicated because it risked war with Mexico and threatened to upset the balance between free and slave states in the Union. President John Tyler began the process near the end of his time in office, and in 1845 Texas officially joined the United States as the 28th state. Mexico, which had never recognized Texan independence, viewed the annexation as an act of aggression. This tension would soon lead to war.
The Oregon Territory
At the same time that the Texas question was being settled, the United States was also in a dispute with Britain over the Oregon Country, a large region stretching from the Rocky Mountains to the Pacific coast. Both nations had claimed the area for years, and American settlers had been traveling there in large numbers along the Oregon Trail throughout the 1840s.
Many Americans wanted the United States to claim all of Oregon up to the latitude of 54 degrees and 40 minutes north, which led to the famous slogan “Fifty-Four Forty or Fight.” In the end, however, President Polk negotiated a compromise with Britain. The Oregon Treaty of 1846 divided the region along the 49th parallel, giving the United States what is now the states of Oregon, Washington, and Idaho, while Britain retained the land to the north, which became part of Canada. It was a peaceful settlement that significantly expanded American territory without going to war with Britain.
The Mexican-American War
The annexation of Texas led directly to the Mexican-American War, which lasted from 1846 to 1848. A dispute over the location of the Texas-Mexico border gave President Polk a reason to ask Congress to declare war on Mexico in May of 1846. Many supporters of Manifest Destiny saw the war as an opportunity to take California and other western territories from Mexico as well.
The war ended with the signing of the Treaty of Guadalupe Hidalgo in February of 1848. Under this treaty, Mexico gave up more than 525,000 square miles (1,360,000 square km) of territory to the United States, including what are now the states of California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado and Wyoming. The United States paid Mexico $15 million in compensation. This acquisition was seen by many Americans as the fulfillment of Manifest Destiny, as the country now stretched from coast to coast.
Not everyone supported the war, however. Prominent figures such as Abraham Lincoln and Ulysses S. Grant were among those who criticized it. Grant, who served in the war as a young officer, later called it one of the most unjust wars ever fought by a stronger nation against a weaker one. Many Whig politicians also opposed the conflict, viewing it as an act of aggression driven by the desire to expand slavery into new territories.
The Gadsden Purchase
The last major piece of continental expansion came in 1853 with the Gadsden Purchase. The United States paid Mexico $10 million for a strip of land in what is now southern Arizona and New Mexico. The main reason for the purchase was to secure a good route for a southern transcontinental railroad. This purchase completed the continental boundaries of the United States as they exist today.
Manifest Destiny and Native Americans
The expansion driven by Manifest Destiny had devastating consequences for Native Americans across the continent. As the United States acquired new territory, the federal government systematically removed Indigenous peoples from their lands to make way for white settlers. The Indian Removal Act of 1830 had already set this process in motion in the east, resulting in events such as the Trail of Tears. As American settlement pushed further west, Native nations on the Great Plains and beyond faced similar displacement, violence, and loss of their way of life.
Manifest Destiny provided a justification for these actions by portraying Native peoples as obstacles to progress rather than as peoples with legitimate claims to their land. In reality, the expansion of the United States came at an enormous cost to the many nations that had lived on the continent for centuries.
Manifest Destiny and Slavery
Manifest Destiny also made the growing conflict over slavery much worse. Every new territory the United States acquired raised the question of whether slavery would be allowed there. Southern states wanted to see slavery expand into the new western lands, while many Northerners wanted to keep it out. This debate became increasingly bitter throughout the 1840s and 1850s.
For instance, the Wilmot Proviso, proposed in 1846, attempted to ban slavery from any territory gained from Mexico, but it failed to pass. The question of slavery in the new territories drove a wedge between the North and South that ultimately could not be resolved, contributing directly to the outbreak of the Civil War in 1861.
Legacy of Manifest Destiny
The era of Manifest Destiny transformed the United States from a collection of states along the Atlantic coast into a continental power stretching from ocean to ocean. In less than 50 years, the country had more than tripled in size through a combination of purchases, treaties, annexation, and war. This growth brought enormous economic opportunity for many Americans and helped make the United States one of the most powerful nations in the world.
At the same time, the legacy of Manifest Destiny is deeply troubling. The expansion of the United States was built on the forced removal of Native peoples, the conquest of Mexican territory, and the labor of enslaved people. The idea that one group had a God-given right to take land from others caused immense suffering that shaped American society for generations.
Today, Manifest Destiny is studied as both a defining force in American history and as an example of how powerful ideas can be used to justify injustice. The phrase itself faded from common use after the Civil War, but the belief in American expansion and influence did not disappear. In the 1890s, the United States began acquiring territory beyond the continent, including Hawaii, Puerto Rico, and the Philippines, in what some historians have called a new phase of Manifest Destiny.
