In late 1847, U. S. forces defeated the Mexican army and occupied the Mexican capital of Mexico City. The Mexican government surrendered to the U. S. and began negotiations to end the Mexican-American War at Guadalupe-Hidalgo, a city north of Mexico City where the government had fled in advance of American troops. There the Treaty of Guadalupe Hidalgo was signed, ending the Mexican-American War. Mexico surrendered all claims to Texas and recognized the Rio Grande River as Texas’ and the U. S.’ southern border. In addition, Mexico turned over thousands of square miles of land to the United States in exchange for $15 million dollars. The land included the present-day states of Arizona and New Mexico as well as Upper California and parts of the present-day states of Nevada, Utah, and Colorado. A long political debate in the U. S. then began over the issue of slavery in the newly acquired territory.