The Gadsden Purchase, also known as the Treaty of La Mesilla, was a treaty signed in 1853 between the United States and Mexico. The treaty was signed in the wake of the Mexican-American War, which ended in 1848 with the signing of the Treaty of Guadalupe Hidalgo. Under the terms of the treaty, the United States paid Mexico $10 million in exchange for a strip of land in what is now Arizona and New Mexico.
The primary purpose of the Gadsden Purchase was to facilitate the construction of a transcontinental railroad. At the time, the United States was expanding westward, and the railroad was seen as a way to connect the country from coast to coast. The land purchased in the Gadsden Purchase was particularly well-suited for this purpose, as it had relatively flat terrain and a mild climate.
In addition to facilitating the construction of the transcontinental railroad, the Gadsden Purchase also had other important consequences. It marked the final major territorial acquisition by the United States, and it helped to establish the current border between the United States and Mexico. Overall, the Gadsden Purchase played a significant role in the expansion and development of the United States in the 19th century.