When the time came to run the boundary line, the American and Mexican commissioners could not agree. So the United States paid ten million dollars more and received an additional strip of land between the Rio Grande and the Colorado rivers. This gave the United States its present southern boundary. This agreement was made in 1853 by James Gadsden for the United States, and the land bought is usually called the Gadsden Purchase.
adj. 附加的,另外的