The
Mexican American War added greatly to the territory of the United States, at the expense of Mexico. James Gadsden, a railroad executive from South Carolina, was President
Franklin Pierce's minister to Mexico. He was instructed to buy land that now forms parts of Arizona and New Mexico for the purpose of providing a southern transcontinental railroad route. The purchase was controversial, as some southerners wanted more land and some northerners opposed the addition of any more potentially slave territory. The final purchase was for 55,000 square miles. It completed the territory that became the contiguous lower 48 states.
