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History of the U.S.-Mexico Border

Jun 6, 2025

Overview

This lecture covered the shifting history of the U.S.–Mexico border, highlighting how it evolved from imaginary lines to today's complex and contentious boundary.

Early Border History

  • For centuries, borders in the Americas were undefined, with European nations and Native tribes contesting control.
  • The border became significant after conflicts, treaties, and surveys starting in the 19th century.
  • In 1801, no official U.S. border existed beyond the Mississippi River.

Expansion and Imagination

  • President Thomas Jefferson envisioned U.S. expansion to the Pacific, initiating it with the 1803 Louisiana Purchase.
  • By 1821, Mexico gained independence and shared a vague border with the U.S., which was largely conceptual.

Mexican-American Conflict and Treaty

  • American settlers illegally migrated into northern Mexico, especially Texas, leading to border disputes.
  • Texas claimed its southern border was the Rio Grande, while Mexico said it was the Nueces River.
  • The Mexican-American War (1846–1848) resulted in the Treaty of Guadalupe Hidalgo, officially establishing the border on paper.

Surveying and Establishing the Line

  • Surveyors faced harsh conditions and violent disputes while marking the border after 1848.
  • The Joint Boundary Commission experienced infighting, financial troubles, and errors due to challenging terrain.
  • The Gadsden Purchase (1853) adjusted the border further south for $10 million.

Persistent Challenges and Changing Borders

  • Apache raids continued, prompting cross-border military agreements.
  • The International Boundary Commission (1889) was created to resolve disputes, especially as the Rio Grande shifted course.
  • Over time, cities, trade, and migration transformed the border from a contested line to a dynamic region.

Modern Border Issues

  • 20th-century economic crises in Mexico and NAFTA spurred migration and industrial growth at the border.
  • Drug trafficking and human movement became prominent issues.
  • The border now tightly binds the two nations, with shared economic and social problems.

Key Terms & Definitions

  • Louisiana Purchase — 1803 U.S. purchase of French territory, doubling the nation’s size.
  • Treaty of Guadalupe Hidalgo — 1848 agreement ending the Mexican-American War and defining the border.
  • Gadsden Purchase — 1853 land acquisition moving U.S. border south for railroad development.
  • International Boundary Commission — Binational body managing ongoing border disputes.

Action Items / Next Steps

  • Review the maps and treaty timelines mentioned.
  • Reflect on how historical border changes shape current U.S.–Mexico relations.