From 1848 to 1854, the Gila River north of this site marked the international border of the United States and Mexico. James Gadsden negotiated the purchase of 38,000 square miles of "wild country" for $15 million in gold, but the agreement was amended to $10 million for 29,640 square miles. The Gadsden Purchase maintained southern railroad and wagon routes while preserving Mexico's link to Baja, California. Today the Gadsden Purchase comprises 24 percent of Arizona's total land area.