How was most of the territory west of Texaas obtained by the U.S.?

Most of the territory west of Texas was obtained by the U.S. through the Mexican-American War (1846-1848) and subsequent treaties. The Treaty of Guadalupe Hidalgo, signed in 1848, resulted in Mexico ceding a vast amount of land, including present-day California, Arizona, New Mexico, Nevada, Utah, and parts of Colorado and Wyoming, to the United States. Additionally, the Gadsden Purchase in 1853 further expanded U.S. territory in the southwest. These acquisitions were driven by the U.S. belief in Manifest Destiny, the idea that it was destined to expand across the continent.