Americans attempted to police the movement of Native peoples by placing them on reservations, but they in no way tried to stop the migration of Mexicans across the newly drawn border. To the contrary, Mexicans—especially after the Chinese Exclusion Act of 1882, which excluded Chinese as a matter of law if not practice—became desirable and exploitable laborers who dug mines, extracted minerals, built railroads, and harvested crops. Nothing about this changed until well into the twentieth century.
