Mexican-American War: A conflict between the United States and Mexico from 1846 to 1848 over territorial disputes. It ultimately resulted in the cession of the New Mexico territories to the United States.
Treaty of Guadalupe Hidalgo: The treaty signed in 1848 that ended the Mexican-American War. It established new boundaries between the United States and Mexico, resulting in Mexico ceding vast amounts of territory including the New Mexico territories.
Manifest Destiny: The belief held by many Americans during the 19th century that it was their destiny or duty to expand across North America from coast to coast. This ideology played a significant role in driving westward expansion and territorial acquisitions like the New Mexico territories.