the name given to a tract of land in the southern part of New Mexico and Arizona, purchased from Mexico by the United States in 1854, through the agency of James Gadsden. It is bounded on the north by the Gila River, on the east by the Rio Grande, on the west by the Colorado and on the south by an arbitrary line. Its average width is about 120 miles, and it includes an area of about 45,535 square miles. The United States paid Mexico $10,000,000 and made other concessions. The treaty was negotiated in 1853 and was ratified in the following year. It caused such opposition in Mexico that Santa Anna was banished.