Manifest Destiny
Manifest Destiny was the 19th-century belief that the United States was destined — even divinely ordained — to expand across the North American continent. It fueled westward migration, the annexation of Texas, and the Mexican-American War in the 1840s.
Manifest Destiny was the widely held 19th-century conviction that the United States had a mission, sanctioned by Providence, to expand its territory and institutions across North America. Journalist John O'Sullivan coined the phrase in 1845, writing of the nation's "manifest destiny to overspread the continent." The idea blended nationalism, a belief in American democratic institutions, and assumptions of cultural and racial superiority.
The doctrine reached its peak in the 1840s. It provided justification for the annexation of Texas (1845), the resolution of the Oregon boundary dispute with Britain (1846), and the Mexican-American War (1846-1848), which ended with the Mexican Cession adding California and much of the present-day Southwest. Expansion carried enormous human costs: Native American nations were displaced from their lands, and Mexican residents of the ceded territories saw their communities absorbed by conquest.
Manifest Destiny also sharpened the sectional crisis. Every new territory raised the question of whether slavery would be permitted there, producing flashpoints like the Wilmot Proviso and the Compromise of 1850 and accelerating the collision that led to the Civil War. After 1865, the same expansionist logic reappeared in the settlement of the West and, later, in arguments for overseas expansion.
The AP U.S. History exam treats Manifest Destiny as a central theme of Period 5 (1844-1877). Expect questions connecting the ideology to Texas annexation, the Mexican-American War, debates over slavery's expansion, and continuity and change in westward expansion after the Civil War.
Key takeaways
- Manifest Destiny was the belief that U.S. expansion across the continent was justified and inevitable; John O'Sullivan coined the term in 1845.
- It drove the annexation of Texas, the Oregon settlement, and the Mexican-American War, which produced the Mexican Cession.
- Expansion came at the expense of Native American nations and Mexican residents of the acquired territories.
- Each new territory reignited the debate over slavery's expansion, deepening sectional conflict before the Civil War.
- AP U.S. History tests Manifest Destiny as a core Period 5 theme linking expansion, war, and the slavery debate.