By 1850, 360,000 Native Americans lived west of the Mississippi River. Over the following decades, many were forced onto reservations as settlers and the US government broke treaties and seized tribal lands. Native American resistance led to armed conflicts like the Sioux victory over Custer at Little Bighorn in 1876. By the 1880s, the US government had established reservations across the West and tried to assimilate Native Americans into white society through measures like the Dawes Act.