Agreement Ending The Mexican-American War
War between Mexico and America, the Mexican War, Spanish Guerra of 1847 or Guerra de Estados Unidos a Mexico („War of the United States against Mexico”), war between the United States and Mexico (April 1846-February 1848) because of the annexation of Texas by the United States in 1845 and a dispute over the end of Texas at the Nueces River (Mexican claim) or the Rio Grande (US). The war, in which American forces were victorious, led the United States to acquire more than 1300,000 square kilometers of Mexican territory, which stretched west of the Rio Grande to the Pacific Ocean. The Treaty of Guadalupe Hidalgo was signed on February 2, 1848 by the United States and Mexico, ending the Mexican war and expanding the borders of the United States by more than 525,000 square miles. In addition to the construction of the Rio Grande as a border between the two countries, the territory acquired by the United States included the states of Texas, California, Nevada, Utah, most of New Mexico and Arizona, as well as parts of Colorado and Wyoming. In exchange, Mexico received $15 million in land compensation and the United States agreed to accept claims by individuals in those territories against the Mexican government. In addition to the sale of land, the contract also provided for the recognition of the Rio Grande as a border between the State of Texas and Mexico.  Land borders were defined by a team of surveyors appointed by Mexican and American officials and published in three volumes as The United States and Mexican Boundary Survey. On December 30, 1853, by mutual agreement, the countries changed the original boundary by increasing the number of terminals from 6 to 53.  Most of these marks were simply piles of stones.  Two subsequent conventions, 1882 and 1889, continued to clarify borders, as some of the marks had been moved or destroyed.  Photographers were taken to document the location of the markers.
These photos are available in Record Group 77, Records of the Office of the Chief Engineers, in NationalArchiv. On November 10, 1845, before the outbreak of hostilities, President James K. Polk sent his envoy John Slidell to Mexico. Slidell had instructions to offer Mexico about $5 million for the territory of Nuevo México and up to $40 million for Alta California.  The Mexican government fired Slidell and refused to meet with him.  Earlier this year, Mexico severed diplomatic relations with the United States, in part on the basis of the interpretation of the 1819 Adams Ons Treaty, under which Mexico, newly independent, claimed to have inherited rights.