How the US Acquired Arizona: The Gadsden Purchase (1853)

The United States acquired the territory that became **Arizona** primarily through the **Gadsden Purchase** of 1853—finalizing the continental US's southern border.

The Treaty

• Parties: USA (President Franklin Pierce, Sec. of War Jefferson Davis) & Mexico (Antonio López de Santa Anna).
• Signed: December 30, 1853 (Mexico City); ratified US Senate April 25, 1854.
• Price: **$10 million** (equivalent ~$380M today).
• Land Ceded: ~29,670 sq mi (76,800 km²) — **southern Arizona** (below Gila River) + **southwestern New Mexico** (bootheel).

Why This Land?

• Transcontinental Railroad: Southern route (via El Paso, Tucson, Yuma) required this corridor—lower elevation, no Rocky Mountain crossing.
• Border Clarity: Resolved ambiguities from Treaty of Guadalupe Hidalgo (1848) after Mexican–American War.
• Santa Anna's Need: Mexico needed funds for army, debt; sold "useless desert."

Prior & Subsequent Steps

• 1848 Guadalupe Hidalgo: US gained CA, NV, UT, AZ north of Gila, NM, CO, WY.
• 1863: Arizona Territory organized (split from NM Territory).
• 1912: Arizona statehood (48th).

Controversy & Legacy

• Criticized as "buying a desert"; later proved mineral-rich (copper, silver).
• Tohono O'odham Nation split by new border.
• Railroad built (Southern Pacific, 1880s)—enabled AZ development.

The Gadsden Purchase completed the lower 48's map—$10M for the final piece.