Manifest Destiny: The belief that it was the destiny of the United States to expand its territory from coast to coast.
Mexican-American War: A conflict between the United States and Mexico from 1846 to 1848, resulting in significant territorial gains for the U.S.
Treaty of Guadalupe Hidalgo: The treaty signed in 1848 which ended the Mexican-American War and granted the United States vast territories including California, Nevada, Utah, Arizona, New Mexico, Texas, and parts of Colorado and Wyoming.