The Treaty of Guadalupe Hidalgo was the agreement signed on February 2, 1848, that ended the Mexican-American War and resulted in Mexico ceding a significant portion of its territory to the United States. This treaty not only marked a pivotal moment in the expansion of U.S. territory but also exemplified the belief in Manifest Destiny, as it fulfilled American ambitions to expand across the continent, leading to further debates about slavery and statehood in the newly acquired lands.