President Franklin Pierce sent Ambassador James Gadsden to Mexico City in 1853. His mission was to buy land from Mexico to the south of the boundaries established by the Treaty of Guadalupe-Hidalgo, which had ended the Mexican-American War of 1846-48. Pierce preferred that Gadsden obtain for the United States a port on the Gulf of California. This would have allowed for more expeditious transport of heavy machinery to copper and silver mines in the Southwest. Mexico, however, refused to grant that option.
The purchase terms that were accepted included lands south of the Gila River and west of the Rio Grande. The treaty settled the dispute over the exact location of the Mexican border west of El Paso, Texas, giving the U.S. claim to approximately 29,000 square miles of land in what is now southern New Mexico and Arizona, for the price of $10,000,000. It established the southwestern boundary of Arizona at Yuma, where it remains today. The Senate ratified the treaty on June 24, 1854.
Tucson had already been occupied by native tribes such as the Pima and the Papagos, as well as by descendants of Spanish explorers. The town was built on the site of the little Pima village of “Stjukshon” (dark spring). In 1775, Irish-born Hugo O’Conor, a member of the Spanish army, established a presidio (fort) on the site. O’Conor did not stay in Tucson but went off with Spanish forces to fight the Apache and Comanche tribes who were attacking the area.
After 1853, Tucson became the only walled city that the United States has ever known. It has since expanded far beyond the original Presidio district.
Tucson’s culture remains mostly Hispanic, but with a good bit of the Irish coming out on St. Patrick’s Day.