From Wikipedia

The Native Americans

Episode Four

Fields of Grass, Sea of Blood

Indian Wars is the name used in the United States to describe a series of conflicts between the colonial settlers or federal government and the native peoples of North America. There's no conclusive evidence to determine how many Native peoples lived in North America before Columbus. David Stannard notes that more conservative demographers cite a figure of about 7 or 8 million inhabitants. Scholars now believe that, among the various contributing factors, infectious disease was the overwhelming cause of the population decline of the American natives. Some estimates indicate case fatality rates of 80-90 % in Native American populations during smallpox epidemics.