The Gadsden Purchase was the last major territorial addition to the contiguous United States, acquiring 29,640 sq mi from Mexico to enable a southern transcontinental railroad.
Key Facts
- Area acquired
- 29,640 square miles (76,800 km²)
- First draft signed
- December 31, 1853
- Treaty took effect
- June 8, 1854
- Primary purpose
- Route for a southern transcontinental railroad
- Railroad completed
- Sunset Route by Southern Pacific, 1881–1883
By the Numbers
Location
Cause → Event → Consequence
The United States sought land south of the Gila River and west of the Rio Grande to build a viable southern transcontinental railroad. The desired corridor required a flatter, more direct route than existing U.S. territory allowed, and the boundary between Mexico and the United States remained disputed in the region, making a formal purchase necessary.
On December 31, 1853, U.S. Minister to Mexico James Gadsden and Mexican President Antonio López de Santa Anna signed the first draft of the treaty. The agreement transferred 29,640 square miles of what is now southern Arizona and southwestern New Mexico from Mexico to the United States in exchange for payment, with the treaty formally taking effect on June 8, 1854.
The purchase provided the land corridor needed for the Sunset Route, later completed by the Southern Pacific Railroad between 1881 and 1883. It also definitively established the modern Mexico–United States border. The acquired territory now encompasses several major Arizona and New Mexico cities, including Tucson and Yuma, and represented the final substantial expansion of the contiguous United States.
Political Outcome
The United States acquired 29,640 square miles from Mexico, finalizing the contiguous U.S. border and securing a route for a southern transcontinental railroad.
The region south of the Gila River was Mexican territory with a disputed border.
The region became U.S. territory, establishing the current Mexico–United States border.