Gadsden Purchase: U.S. Secures Southern Railroad Route

American ambassador James Gadsden signed a treaty with Mexican President Antonio Lopez de Santa Anna on December 30, 1853, purchasing 29,670 square miles of desert territory south of the Gila River for $10 million. The Gadsden Purchase was the last major territorial acquisition by the United States in the contiguous lower 48 states, and its purpose was entirely practical: the flattest feasible route for a transcontinental railroad to the Pacific ran through land that still belonged to Mexico after the 1848 Treaty of Guadalupe Hidalgo. The purchase was driven by Secretary of War Jefferson Davis, a Mississippi senator and future president of the Confederacy, who championed a southern transcontinental railroad route that would connect New Orleans to San Diego and shift economic power toward the slaveholding South. Davis persuaded President Franklin Pierce to send Gadsden, a South Carolina railroad executive, to negotiate with Santa Anna, who desperately needed cash to fund his latest return to power and suppress domestic revolts. The original deal called for a much larger territory at $50 million, including most of northern Sonora and Chihuahua plus Gulf of California access. Northern senators, suspicious of the slavery connection, slashed the territory in half and reduced payment to $10 million. The final boundary created the distinctive notch in the Arizona-New Mexico border that is visible on any map of the United States. The irony of the Gadsden Purchase is that the southern railroad route it was designed to facilitate was not built for decades. The Civil War intervened, and the first transcontinental railroad was completed in 1869 along a central route through Nebraska, Wyoming, and Utah. The Southern Pacific Railroad finally crossed the purchased territory in 1881, connecting Los Angeles to El Paso. The region today encompasses Tucson, Yuma, and southwestern New Mexico.