Gadsden Purchase

The Gadsden Purchase is a 29,670-square-mile 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 U.S. wanted to build a transcontinental railroad along a deep southern route, which the Southern Pacific Railroad later completed in 1881–1883. The purchase also aimed to resolve other border issues.

The first draft was signed on December 30, 1853, by James Gadsden, U.S. ambassador 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 transmitted 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 and Yuma are on territory acquired by the U.S. in the Gadsden Purchase.

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