How much did we pay for the Gadsden purchase?

Milestones: 1830-1860. Gadsden Purchase, 1853-1854. The Gadsden Purchase, or Treaty, was an agreement between the United States and Mexico, finalized in 1854, in which the United States agreed to pay Mexico $10 million for a 29,670 square mile portion of Mexico that later became part of Arizona and New Mexico.