Land Ceded by Mexico in the Mexican-American War & Gadsden Purchase

The Mexican-American War (1846–1848) and the subsequent Gadsden Purchase (1854) transferred vast territories from Mexico to the United States—reshaping the map of North America.

Treaty of Guadalupe Hidalgo (1848)

Mexico ceded ~525,000 square miles—about 55% of its pre-war territory—in exchange for $15 million and US assumption of $3.25 million in claims by US citizens against Mexico. The cession included all or parts of present-day:

• California
• Nevada
• Utah
• Arizona (north of Gila River)
• New Mexico (most)
• Colorado (western)
• Wyoming (southwestern)
• Texas (boundary confirmed at Rio Grande, not Nueces River)

Gadsden Purchase (1854)

Negotiated by US Minister James Gadsden, this added ~29,670 square miles for $10 million (reduced from $15M after Senate debate). The land—south of the Gila River in present-day southern Arizona and southwestern New Mexico—secured a viable southern transcontinental railroad route (later the Southern Pacific).

Total Transfer

~554,670 square miles—an area larger than France, Germany, and Spain combined. The US paid $25 million total ($15M + $10M) plus assumed claims.

Context & Consequences

• Completed the continental US (except Alaska, 1867).
• Intensified the slavery expansion debate → Civil War catalyst.
• Displaced Mexican landowners; Native nations (Apache, Comanche, Navajo, etc.) faced accelerated US military conquest.
• Established the modern US-Mexico border (further adjusted by 1905 Banco Convention and 1963 Chamizal Treaty).

The war and purchase were driven by "Manifest Destiny," Southern railroad ambitions, and geopolitical rivalry with Britain. The territories gained became the engine of US western economic expansion—gold, silver, copper, agriculture, oil, and eventually tech and aerospace.