Gadsden Purchase

The Gadsden Purchase (Spanish: Venta de La Mesilla, lit. 'La Mesilla sale'), also known as the Treaty of Mesilla, is a 29,640-square-mile (76,800 km2) region of present-day southern Arizona and southwestern New Mexico that the United States acquired from Mexico. The first draft was signed on December 31, 1853, by James Gadsden, US Minister to Mexico, and by Antonio López de Santa Anna, president of Mexico. The treaty took effect on June 8, 1854. The purchase included lands south of the Gila River and west of the Rio Grande, where the United States wanted to build what is now known as the Sunset Route, a transcontinental railroad which the Southern Pacific Railroad later completed in 1881–1883. These lands allowed the railroad to follow a flatter and more direct route, lowering its anticipated costs and allowing faster completion, and particularly encouraging a route to a southern port. The purchase also clearly defined the current Mexico–United States border. The Santa Anna government, in financial distress, accepted the sale, which brought Mexico 10 million dollars (equivalent to 270 million dollars in 2023). Following the devastating loss of Mexican territory to the U.S. in the Mexican-American War (1846–48) and the ongoing unauthorized military expeditions in the region led by the territorial governor of New Mexico and known filibuster William Carr Lane, some historians argue that Santa Anna may have calculated that it was better to cede territory through a treaty and receive payment rather than having the United States simply seize the territory. The Gadsden Purchase was the last substantial territorial enlargement of the contiguous United States. The Arizona cities of Yuma, Tucson, Nogales, Sierra Vista, Tombstone, and Douglas, as well as the New Mexico city of Deming are on territory acquired by the U.S. in the Gadsden Purchase.