Today in History: The U.S. Agrees to Purchase 45,000 Square Miles of Land from Mexico

by M.C. Millman 

The Gadsden Purchase was an agreement between the United States and Mexico, which took place on December 30, 1853, and was finalized in 1854. 

The United States agreed to pay Mexico $10 million for  29,670 square miles of Mexico. This section later became part of Arizona and New Mexico. At the time, most policymakers thought the United States would eventually expand further into Mexico, but that was not the case, and the Gadsden Purchase constituted the United States' southernmost border until today.

The land that was part of Gadsden's Purchase was necessary for a southern transcontinental railroad and was also an attempt at resolving any remaining tension resulting from the Mexican-American War.

The deal was negotiated by James Gadsden, the new U.S. Minister to Mexico at the time under President Franklin Pierce. Gadsden was instructed to negotiate a border with Mexican President Antonio de Santa Anna that would provide a route for a southern railroad, among other things. 

Desperate for money to fund an army to fight ongoing rebellions, Santa Anna signed a treaty with Gadsden on December 30, 1853. The treaty gave 45,000 square miles of New Mexico territory to the United States for  $15 million. The treaty was revised on April 25, 1854, reducing the amount paid to $10 million and the land purchased to 29,670 square miles. Santa Anna signed the new treaty on June 8, 1854.