General Antonio López de Santa Anna returns from exile in 1853, and with the help of rebellious conservatives once again becomes Mexico’s ruler, declaring himself dictator for life with the title "Most Serene Highness".

As Mexico is willing to sell additional lands to the United States government, the Pierce administration sends American diplomat James Gadsden to negotiate a treaty whereby Mexico cedes a rectangular strip of about 29,640 square miles (76,760 kilometers) in the Mesilla Valley south of the Gila River for ten million dollars.

Southerners, whose Democratic party has put Franklin Pierce in office, plan on using the so-called Gadsden Purchase for a railway route to the Pacific.

Gadsden, a South Carolinian, is an ardent supporter of a southern railroad, but he envisions it being built to Charleston, South Carolina.

Gadsden is interested in this purchase since he has acquired shares of the railroad company that would unite Texas and California.

As originally envisioned, the purchase would have encompassed a much larger region, extending far enough south to include most of the current Mexican states of Coahuila, Chihuahua, Sonora, Nuevo Leon, and Tamaulipas as well as all of the Baja California peninsula.

These original boundaries had been opposed not only by the Mexican people, but also by anti-slavery U.S.

Senators who see the purchase as tantamount to the acquisition of more slave territory.

Outraged at the reduced size of the purchase, ...