The Treaty of Guadalupe Hidalgo ended the Mexican-American War. Mexico ceded the Texas-claimed areas as well as a large area of land consisting of all of present-day California, Nevada, and Utah, most of Arizona, and portions of Colorado, New Mexico, and Wyoming (1848)
The name Doughboy originates from possibly as early as the Mexican-American War of 1846-8, possibly from the dust which caked them men as they marched or possibly a reference to the bread rations given to troops during the war. The nickname was most commonly used during the First World War although it remained in use during the Second World War.
The Mexican-American war started along the border of the Rio Grande on April 25, 1846, when Mexican cavalry attacked a group of U.S. soldiers. On February 2, 1848, the Treaty of Guadalupe Hidalgo was signed after a series of U.S. victories. Mexico lost about 1/3 of its territory which included California, Utah, Nevada, Arizona, and New Mexico. http://www.britannica.com/EBchecked/topic/379134/Mexican-American-War