Territories Mexico Lost to the United States After the Mexican‑American War

The Treaty of Guadalupe Hidalgo (1848) ended the war and forced Mexico to cede roughly 55% of its pre‑war territory to the U.S. The lands comprise all or parts of present‑day:

• California
• Nevada
• Utah
• Arizona (most of present state)
• New Mexico (most of present state)
• Colorado (western portion)
• Wyoming (southwestern corner)

Additional Note

The Gadsden Purchase (1854) later added a strip of southern Arizona and New Mexico for $10 million, finalizing the current U.S.–Mexico border.