The Gadsden Purchase (also known as the Gadsden Treaty or the Mesilla Valley Purchase) was a land transfer agreement between the United States and Mexico, negotiated by James Gadsden, the U.S. ambassador to Mexico. It was signed on December 30, 1853, and ratified on June 29, 1854. The treaty resulted in the United States acquiring about 29,670 square kilometers (11,460 sq mi) of Mexican territory for $10 million.
The primary reason for the Gadsden Purchase was to acquire a strip of land in southern Arizona and New Mexico to construct a transcontinental railroad. This would allow for a shorter and more direct route between the Atlantic and Pacific coasts than would be possible if the United States had to build its railroad through the rugged Sierra Nevada mountains. The acquisition of the Gila River Valley, which is rich in agriculture, was also considered a significant benefit to the United States.