Gadsden Purchase
After 1848, Mexico and the United States did not agree where the border was. Both countries claimed the Mesilla Valley as part of their own country. Businessmen from the southern states wanted to build a new transcontinental railroad that would cross the southern part of the country. They wanted the railroad to go through the Mesilla Valley. Jefferson Davis, who at that time was the US Secretary of War, supported that idea. James Gadsden was sent to buy the land from Mexico. He wanted to buy much more land, including Tamaulipas, Coahuila, Nuevo Leon, and parts of Chihuahua and Sonora, but the Mexican president, Antonio Lopez de Santa Anna, did not want to sell it to him.