Beginning in 1846, the United States went to war with Mexico over control of lands in what are now California, Texas, and New Mexico.
The Americans won the Mexican War (1846-1848), and, in the peace treaty, the United States was given this territory.
Almost immediately, non-Indian Americans flooded into the lands of the California Indians. Some of the Americans were settlers, attracted by the rich lands and pleasant climate.
Others were miners, who flocked to California hoping to strike it rich in the Gold Rush.