Lecture 4a: Manifest Destiny and the Slave Power Conspiracy

Major Questions Discussed

• What was manifest destiny?
• How did the U.S. expand its territorial holdings in the 1840s?
• What was the slave power conspiracy?
• Why was the war against Mexico controversial?

Manifest Destiny

• Coined by John O'Sullivan, a New York City journalist.
• America’s god-given duty to expand westward, from the Atlantic to the Pacific Ocean.
• Justified by the belief in racial superiority, paternalism (civilizing Native Americans and Mexicans), and anti-Catholic sentiment.

Advocates of Manifest Destiny

• Northern merchants and industrialists supported it for commerce, natural resources, and trade with East Asia.

Visual Representation

• Thomas Nast’s painting: Light vs. Dark, yeoman farmers, industrial progress vs. Native Americans and wilderness.

Territorial Acquisitions in the 1840s

Texas

• Texas War for Independence, followed by President James K. Polk's annexation process.
  • Fear of British annexation and abolition of slavery in Texas.
  • Balance with anti-slavery advocates: potential admittance of Oregon Territory as a free state.

Oregon (1846)

• Slogan: “54°40’ or Fight!” (refers to the northern border with British Columbia).
• Polk’s negotiation with Britain: USA ceded claims in British Columbia; Britain ceded claims to Oregon Territory.
• New top border at 48° North.

Second Seminole War (1835-1842)

• Seminole removal due to threat to southern plantation owners (destination for runaway slaves).
• Indian Removal Act of 1830 included Seminoles.
• War was costly and largely unsuccessful, several Seminoles evaded capture.

War with Mexico (1846-1848)

• Polks's attempt to buy New Mexico failed, leading to border disputes over Texas.
  • U.S. claimed Rio Grande as the border; Mexico claimed Nueces River.
  • This led to the Mexican-American War.

Controversy and Opposition

• Slave Power Conspiracy: Northerners feared southern control of the federal government to legalize slavery everywhere.
  • Evidence: Three-Fifths Compromise, balance in the Senate, and doe faces (Northern Democrats siding with the South).
• Miscegenation Fear: Concerns about inter-racial relationships degrading the white race.
• Prominent opponents: Abraham Lincoln (anti-war speech), Henry David Thoreau (tax protest).

Spoils of War

• Debates over how much land to take and whether new lands would allow slavery.
• Wilmot Proviso: Proposed to ban slavery in new territories, didn't pass but intensified sectional tensions.
• Treaty of Guadalupe Hidalgo (1848): Ended the war, US paid $18M, gained significant territory.

Consequences

• Increased Native American conflicts in newly acquired territories (e.g., Indian Wars).
• Gold discovered in California (1848), leading to statehood as a free state (1850).
• Governorship efforts to exterminate Native Americans in California.
• Political Fallout: Rise of Free Soil Party (1848), pushing for free labor and opposing slavery extension.