When the US won the Mexican-American War in 1848, Mexico was forced to cede nearly half of its territory—land that later made up California, Nevada, Utah, Arizona, New Mexico, Colorado, and Wyoming—for $15 million as part of the Treaty of Guadalupe Hidalgo. The people living there did not cross any border or migrate anywhere. Instead, the border crossed them, forcing US citizenship on them overnight with the promise they could keep the land they owned.
