5.3 The Mexican–American War

Overview

• Significance of the Mexican-American War:

  • Key moment in American expansion.

  • Directly connects Manifest Destiny to growing crisis over slavery.

  • Dramatically expanded U.S. territory.

  • Forced Americans to confront difficult questions about national identity, citizenship, and slavery.

  • A foundational conflict for understanding the sectional tensions leading to the Civil War.

The Road to War

• Texas, Independence, and Annexation:

  • Seeds of conflict planted years before actual fighting began.

  • Relationship shaped by:

  • Competing land claims.

  • Cultural differences.

  • Disagreements about borders.

  • Texas War of Independence (1835-1836):

  • Key battles: Alamo, Goliad (where 400+ Texan prisoners were executed), San Jacinto.

  • Republic of Texas existed as an independent nation from 1836 to 1845.

  • Mexico never recognized Texas independence, considering it Mexican territory.

  • U.S. annexation of Texas in 1845 exacerbated tensions.

Causes of the War

• Multiple Factors Contributing to the Conflict:

  • Not simply land hunger; rooted in deeper interests:

  • Economic interests.

  • Political calculations.

  • Cultural attitudes towards Mexico.

  • Border Disputes:

  • U.S. claimed the Rio Grande as border; Mexico insisted on the Nueces River (about 150 miles north).

  • Viewed U.S. annexation of Texas in 1845 as aggression.

  • President James K. Polk's Expansionist Agenda:

  • Desire for Pacific ports and economic interests in California.

  • Ordered General Zachary Taylor to position troops along the disputed territory.

  • April 1846 Incident:

    • Mexican forces attacked American troops in disputed zone.

    • Polk declared, "American blood has been shed on American soil."

The War and Its Conduct

• Overview:

  • First major conflict fought mostly on foreign soil by the U.S.

  • U.S. advantages: resources and technology; however, Mexican forces were determined defenders.

  • Timeline of War (1846–1848):

  • American forces invaded Mexico from multiple fronts.

    • General Zachary Taylor led the northern campaign along the Rio Grande.

    • General Winfield Scott landed troops at Veracruz from the sea.

  • Captured Mexico City in September 1847.

  • Superior American artillery and leadership proved decisive.

  • Impact on Military Leaders:

  • War made heroes of future Civil War generals such as Robert E. Lee and Ulysses S. Grant.

Treaty of Guadalupe Hidalgo

• Signing and Terms:

  • Signed February 2, 1848; officially ending the war.

  • Mexico ceded approximately 525,000 square miles of territory to the U.S.

  • Ceded lands included current California, Nevada, Utah, Arizona, New Mexico, parts of Colorado, Wyoming, Kansas, and Oklahoma.

  • U.S. paid Mexico $15 million in compensation and took on $3.25 million in claims American citizens had against the Mexican government.

  • Guarantees for Mexicans in Ceded Territories:

  • Option to return to Mexico or become U.S. citizens.

  • Protection of property rights.

  • Freedom to practice Catholic religion.

  • Many rights later violated or ignored.

Consequences and Significance

• Long-Term Impact:

  • The war reshaped American politics, worsened tensions between North and South, and affected various cultural groups under new governance.

• Political Outcomes:

  • Victory fueled American confidence in military and expansionist destiny.

  • Heroes Zachary Taylor and Winfield Scott transitioned to political figures.

  • Intensified debates over slavery in new territories:

  • Wilmot Proviso (1846) attempted to ban slavery in territories acquired from Mexico; passed in House but failed in Senate, highlighting the North-South divide.

• Cultural Group Impact:

  • Approximately 75,000-100,000 Mexican citizens became U.S. residents overnight.

  • Many Mexican Americans lost land through legal manipulation despite treaty protections.

  • Native American tribes faced increased pressure from American settlement; California Native populations dramatically declined post-conquest.

• International Relations:

  • Established lasting resentment in Mexico towards the U.S.

  • U.S. emerged as a dominant power in North America, shifting foreign policy focus toward the Pacific.

  • Resulted in the later Gadsden Purchase (1853) for southern Arizona and New Mexico.

Vocabulary

• American Indians: Indigenous peoples of North America prior to European contact.

• Diplomatic Negotiations: Formal discussions between leaders to resolve conflicts.

• Economic Self-Sufficiency: Ability to meet economic needs independently, altered for Mexican Americans post-acquisition.

• Mexican-American War: Conflict (1846-1848) resulting in U.S. territorial gains.

• Mexicans: People of Mexican descent in U.S.-acquired territories, facing altered circumstances.

• Slavery: Institution of forced labor exploited for economic gain.

• Territorial Expansion: Acquisition of new lands into a nation's control, often through military victory or negotiation.