The Anasazi culture of prehistoric American Indians developed and flourished, ca. 800–1100, in the Southwest near the present-day borders of Arizona, New Mexico, Colorado, and Utah. Pueblo tribes later developed from the Anasazi.
Native American populations in New England, with no immunity to European diseases, were nearly eradicated by a mysterious epidemic—likely smallpox. Between 1616 and 1619, the population of the Massachusett and other Algonquin tribes was reduced by as much as 90 percent by disease.
Mississippian culture grew in the southern Mississippi River Valley. The Mississippian American Indians were farmers and mound builders, and the culture spread along rivers through modern-day central and eastern North America. Some aspects of Mississippian life grew out of earlier regional cultures, but the Mississippians were also largely influenced by contact with Mayan and Zapotec traders.
Hohokam culture of prehistoric American Indians developed in the Southwest, ca. 600. Hohokam culture grew along the Gila and Salt Rivers, and Hohokam people created irrigation canals that allowed for major agricultural development.
A virgin soil epidemic occurs when bacteria or viruses are introduced into an area where no similar diseases have ever occurred before. Lacking even partial immunity, populations are devastated by such epidemics. Many scholars believe that the severity of Native American loss of life during the first decades of European colonization was due to the fact that these were virgin soil epidemics.