Heimler's History: Mexican American War

Overview

• Topic: Causes and Effects of the Mexican American War
• Unit: AP U.S. History Unit 5
• Key Question: What were the causes and effects of the Mexican American War?

Causes of the Mexican American War

Background

• Texas declared independence from Mexico in 1836.
• Tensions cooled post-conflict but reignited when Texas sought U.S. annexation.
• U.S. Presidents Jackson, Van Buren, Harrison, and Tyler initially opposed annexation.

Annexation

• James K. Polk (President in 1845):
  • Advocated for Texas annexation as part of his election campaign.
  • Annexation process began under President Tyler but was influenced by Polk’s election.
  • Mexico opposed the annexation of Texas.

Diplomatic Efforts

• John Slidell's Mission to Mexico:
  • Attempted to purchase New Mexico and California.
  • Sought to settle the southern border dispute (Nueces River vs. Rio Grande).
  • Both objectives were rejected by Mexico.

Conflict

• 1846: Polk advanced American troops to the Rio Grande, leading to conflict with Mexican troops; 11 Americans killed.
• Result: Polk’s request for war was granted by Congress on May 13, 1846.

Effects of the Mexican American War

Territorial Gains

• Treaty of Guadalupe Hidalgo (1848):
  • Established the Rio Grande as Texas's southern border.
  • Mexican Cession: California and New Mexico ceded to the U.S. for $15 million.
  • Gadsden Purchase (1853) added more land, resulting in Mexico losing over half its territory.

Political and Social Impact

• Wilmot Proviso (1846):
  • Proposed banning slavery in new territories gained; was voted down.
  • Highlighted tensions over slavery; seen as a precursor to the Civil War.

Impact on Residents

• Mexican and Indian Residents:
  • Mexicans granted U.S. citizenship as per the Treaty of Guadalupe Hidalgo.
  • Indians denied citizenship; faced civil rights issues like voter discrimination and educational segregation.

Conclusion

• The Mexican American War had significant territorial, political, and social consequences.
• It exacerbated tensions over slavery and impacted civil rights for non-European residents.

Note: These points cover what you need to know for Unit 5, Topic 3 of AP U.S. History.