Gadsden Purchase

The Gadsden Purchase (Spanish: Venta de La Mesilla "La Mesilla sale") 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 by the Treaty of Mesilla, which 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 the construction of what is now known as the Sunset Route, a transcontinental railroad, to be carried out, which the Southern Pacific Railroad later completed in 1881–1883. This allowed for the railroad's construction to be shorter, easier, and straighter. Without said purchase, the railroad's expansion would have taken longer and been more expensive. The purchase also aimed to resolve other border issues.

The first draft was signed on December 30, 1853, by James Gadsden, U.S. Minister to Mexico, and by Antonio López de Santa Anna, president of Mexico. The U.S. Senate voted in favor of ratifying it with amendments on April 25, 1854, and then sent it to President Franklin Pierce. Mexico's government and its General Congress or Congress of the Union took final approval action on June 8, 1854, when the treaty took effect. The purchase was the last substantial territorial acquisition in the contiguous United States, and defined the Mexico–United States border. The Arizona cities of Tucson, Yuma and Tombstone are on territory acquired by the U.S. in the Gadsden Purchase.

The financially strapped government of Santa Anna agreed to sell the territory for $10 million (equivalent to $270 million in 2024). After the devastating loss of Mexican territory to the U.S. in the Mexican–American War (1846–48) and the continued unauthorized military expeditions in the zone led by William Carr Lane, New Mexico territorial governor and noted filibuster, some historians argue that Santa Anna may have calculated it was better to yield territory by treaty and receive payment rather than have the territory simply seized by the United States.

As the railroad age evolved, business-oriented Southerners saw that a railroad linking the South with the Pacific Coast would expand trade opportunities. They thought the topography of the southern portion of the original Mexican Cession was too mountainous to allow a direct route. Projected southern railroad routes tended to veer to the north as they proceeded eastward, which would favor connections with northern railroads and ultimately favor northern seaports. Southerners saw that to avoid the mountains, a route with a southeastern terminus might need to swing south into what was still Mexican territory.

The administration of President Pierce, strongly influenced by Secretary of War Jefferson Davis, a Southerner from Mississippi, saw an opportunity to acquire land for the railroad, as well as to acquire significant other territory from northern Mexico. In those years, the debate over slavery in the United States entered into many other debates, as the acquisition of new territory opened the question of whether it would be slave or free territory; in this case, the debate over slavery ended progress on construction of a southern transcontinental rail line until the early 1880s, although the preferred land became part of the nation and was used as intended after the Civil War.

In January 1845, Asa Whitney of New York presented the United States Congress with the first plan to construct a transcontinental railroad. Although Congress took no action on his proposal, a commercial convention of 1845 in Memphis took up the issue. Prominent attendees included John C. Calhoun, Clement C. Clay Sr., John Bell, William Gwin, and Edmund P. Gaines, but James Gadsden of South Carolina was influential in the convention's recommending a southern route for the proposed railroad. The route was to begin in Texas and end in San Diego or Mazatlán. Southerners hoped that such a route would ensure Southern prosperity, while opening the "West to southern influence and settlement".

Southern interest in railroads in general, and the Pacific railroad in particular, accelerated after the conclusion of the Mexican–American War in 1848. During that war, topographical officers William H. Emory and James W. Abert had conducted surveys that demonstrated the feasibility of a railroad's originating in El Paso or western Arkansas and ending in San Diego. J. D. B. DeBow, the editor of DeBow's Review, and Gadsden both publicized within the South the benefits of building this railroad.

Gadsden had become the president of the South Carolina Canal and Rail Road Company in 1839; about a decade later, the company had laid 136 miles (219 km) of track extending west from Charleston, South Carolina, and was $3 million (equivalent to $88 million in 2024) in debt. Gadsden wanted to connect all Southern railroads into one sectional network. He was concerned that the increasing railroad construction in the North was shifting trade in lumber, farm and manufacturing goods from the traditional north–south route based on the Ohio and Mississippi rivers to an east–west axis that would bypass the South. He also saw Charleston, his home town, losing its prominence as a seaport. In addition, many Southern business interests feared that a northern transcontinental route would exclude the South from trade with the Orient. Other Southerners argued for diversification from a plantation economy to keep the South independent of northern bankers.