Grandson of Revolutionary War hero Christopher Gadsden, creator of the Gadsden flag, James Gadsden was a southern firebrand from South Carolina. In 1831 he supported Nullification and in 1850 he called for the secession of South Carolina on the admission of California into the Union as a free state. In 1851 he sponsored efforts in California to split the state with southern California becoming a slave state. Dying in 1858 he did not live to see the creation of the Confederacy or the destruction of it and slavery.
Along with his political activities Gadsden from 1840-1850 was president of the South Carolina Railroad. He envisaged a southern transcontinental railroad linking Charleston, South Carolina to the Pacific at San Diego. A major problem for such a railroad was that the land in the New Mexico Territory, including most of what would become Arizona, was thought to be unsuitable for the construction of the railroad. Land south of the Gila river and west of the Rio Grande in what is today southern Arizona looked much more promising.
James Gadsden, the most unlikeliest of men for the role of diplomat, was appointed by President Franklin Pierce, ever sympathetic to southern firebrands, to attempt to negotiate a treaty with Mexico for the purchase of such land. Santa Anna was in what would turn out to be his last term as President\Dictator of Mexico. The negotiations began on the wrong foot when Gadsden bluntly told Santa Anna that the northern Mexican provinces would eventually secede from Mexico anyway, so he might as well sell the land to the US now. However, Santa Anna needed money. After considerable haggling, Santa Anna agreed to sell 38,000 square miles of desert to the US for the southern railroad.
The treaty went to the United States Senate for ratification. There it got entangled in the debate over slavery raised by the Kansas-Nebraska Act fight, northern anti-slavery senators fearing that this was merely an effort to get more land on which to erect slave states. On April 25, 1854, after one failed attempt,the treaty passed the Senate with modifications, the most significant of which was the reduction of the purchase price to ten million dollars and a reduction of the amount of land purchased to 29,000 square miles. Santa Anna accepted the modifications and the treaty went into effect.
The treaty was unpopular in Mexico, although the land was widely regarded as worthless. Kit Carson who explored the area claimed that it was land on which even a wolf could not earn his living. In 1855 Santa Anna was toppled from power and fled to Cuba. The treaty was little more popular in the US where the common opinion was that the government had been taken by Santa Anna, paying a large sum of money for waste land infested by Apaches.