James Gadsden was sent to Mexico with several points of negotiation as well as a wide budget. He was authorized to offer Mexico up to $50 million for California and as much as $15 million for the part of northern Mexico that the U.S. wanted for a railroad. While Santa Anna refused to sell California, he was willing to give up a part of Mexico's northern territory.
Santa Anna agreed to sell 45 thousand square miles of land to the tune of $15 million. In addition, the United States agreed to continue doing their best to protect Mexico from Native American attacks, while Mexico agreed to no longer hold them financially liable for any damages. Gadsden and the Mexican president signed this initial agreement on December 30, 1853.