George Brown Tindall and David E. Shi, eds., America: A Narrative History, 5th ed., Vol. 1 (New York: W. W. Norton and Company, 1999), 693.
During the 1850s, the only land added to the United States was a barren stretch of some 30,000 square miles south of the Gila River in present New Mexico and Arizona. This Gadsden Purchase of 1853, in which the United States paid Mexico $10 million, was made to acquire land offering a likely route for a Pacific railroad. The idea of building a railroad linking together the new continental domain of the United States, though a great national goal, spawned sectional rivalries in still another quarter and reopened the slavery issue. Among the many transcontinental routes projected, the four most important were the northern route for Milwaukee to the Columbia River, a central route from St. Louis to San Francisco, anther from Memphis to Los Angeles, and a more southerly route from New Orleans to San Diego via the Gadsden Purchase.