This book offers a comprehensive analysis of circular village forms. Between A.D. 1000 and 1635, the inhabitants of southwestern Pennsylvania and portions of adjacent states - known to archaeologists as the Monongahela Culture or Tradition - began to regularly reside in ring-shaped village settlements. These circular settlements consisted of dwellings around a central plaza. A cross-cultural and cross-temporal review of archaeological, ethnohistorical, and ethnographic cases demonstrates that this settlement form appeared repeatedly and independently worldwide, including throughout portions of the Eastern Woodlands, among the Plains Indians, and in Central and South America. Specific archaeological cases are drawn from Somerset County, Pennsylvania, which has the largest number of completely excavated Monongahela villages. Most of these villages, excavated in the 1930s as federal relief projects, were recently dated. Full analysis of the extensive excavations reveals not only the geometric architectural patterning of the villages, but enables an analysis of the social groupings, population estimates, and economic status of residents that inhabited the circular villages. Circular patterning can be revealed at less fully excavated archaeological sites. Focused test excavations can help confirm circular village plans without extensive and destructive excavations.