Manifest Destiny, Explained [APUSH Review]

Manifest Destiny and Westward Expansion

The video explains how westward expansion became a defining feature of American life and a major source of conflict beginning in 1844. The push to settle and control territory west of the Mississippi helped drive disputes over slavery and territory, conflict with Indigenous peoples, and ultimately the Civil War.

Why Westward Migration Mattered

• Americans had been moving west since the colonial period. British restrictions on settlement beyond the Appalachian region helped fuel colonial resentment; after the Revolution, Americans gained access to western lands.
• The 1803 Louisiana Purchase greatly expanded U.S. territory and opened millions of acres to settlement.
• Southern cotton growers sought new land because cotton farming depleted soil and demand for the crop remained high.
• The West was also viewed as a “pressure release valve”: migration could ease population pressures and social tensions in more settled parts of the country.
• Together, these ideas helped make the frontier part of American identity. Migration accelerated during this period for both ideological and practical reasons.

Ideological Motivation: Manifest Destiny

• Manifest Destiny was a nationalist belief, popularized by newspaper editor John L. O’Sullivan, that God had given the United States a mission to spread across North America, from the Atlantic to the Pacific.
• Supporters argued that American liberty and self-government were superior and should be extended across the continent, regardless of the cost.
• This belief justified aggressive acquisition of Indigenous lands. Many Americans viewed Native peoples as obstacles to progress and wrongly assumed that taking their land would benefit them.
• The video links Manifest Destiny to the Mexican-American War, conflict over slavery that contributed to the Civil War, and violence against Indigenous peoples.

Practical Reasons for Westward Expansion

Economic Opportunity and Natural Resources

• Texas: Its vast plains attracted Southern planters seeking fertile land. The United States annexed Texas in 1845; the annexation and related disputes helped lead to war with Mexico. The spread of slavery into Texas created additional political conflict.
• Oregon: The territory was jointly occupied by the United States and Great Britain under an 1818 agreement. Reports of fertile soil in the Willamette Valley encouraged migration along the Oregon Trail. About 350,000 American settlers had arrived by 1860.
• “54°40′ or Fight”: James K. Polk’s campaign slogan referred to the northern boundary claimed by the United States and suggested a willingness to fight Britain over Oregon.
• California: Gold was discovered there in 1848, triggering the California Gold Rush and a rapid influx of American settlers. California was then Mexican territory.

Federal Policies Encouraging Settlement

• Preemption Act (1841): Allowed squatters on western federal land to buy up to 160 acres before public sale, at a low price, if they lived on and improved the land. The law helped encourage settlement, including in Kansas and Nebraska.
• Homestead Act (1862): Offered settlers 160 acres of western federal land without charge if they lived on and improved it for at least five years. The video notes that the departure of Southern lawmakers during the Civil War made passage possible and helped limit future Southern influence over western lands.
• These policies contributed to the organization and settlement of most remaining western territory by 1890, when the frontier was declared closed.

Religious Refuge

• After the murder of their founder, Joseph Smith, the Mormons sought a place where they could practice their religion more safely.
• In 1847, under Brigham Young, they traveled west and settled near the Great Salt Lake in Utah, then Mexican territory. The video says roughly 16,000 Mormons had settled there within a few years.

Trade with Asia

• As U.S. trade with China declined, the government sought greater access to Japan, which had restricted foreign trade for about two centuries.
• In 1854, Commodore Matthew Perry arrived with warships and threatened force unless Japan opened ports to U.S. trade. Japan agreed to limited trade at two ports.

Consequences and Conflicts

• Western lands were already home to many Indigenous peoples. Federal settlement policies and migration violated treaties that had designated some lands as Indigenous territory, displacing Native communities.
• Some groups, including the Comanches in southern Texas, resisted migration violently, but the expanding United States ultimately conquered Indigenous resistance.
• The struggle to acquire territory and determine whether slavery would expand into it sharpened sectional conflict. In the video’s account, the drive west helped set the stage for the Civil War.

Speakers and Sources Featured

• Heimler (narrator): Presents the lesson and explains the historical developments.
• John L. O’Sullivan: Quoted on Manifest Destiny and the United States’ supposed divine mission to possess the continent.
• Historical figures mentioned: James K. Polk, Thomas Jefferson, Brigham Young, Joseph Smith, and Commodore Matthew Perry. They are discussed in the narration; the subtitles do not identify them as speaking.