The Treaty of Guadalupe Hidalgo was signed on February 2, 1848. This treaty officially ended the US-Mexican War. This Treaty added 525,000 square miles to the United States. The United States ended up paying Mexico $15 million for the area known as the Mexican Cession. This area included present-day Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. Mexico also recognized the Rio Grande as the official southern border.