Map of the Mexican Cession. The territories ceded by Mexico to the U.S. in 1848 in the Treaty of Guadalupe Hidalgo, which ended the Mexican-American War (1846 – 1848). The land lost equalled one third of Mexico’s total territory — and became California and the Southwestern United States. By Kballen – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3841280