At the confluence of the Illinois, the Missouri, and the Mississippi Rivers lies the "American Bottom," a broad floodplain that prehistoric peoples inhabited for millennia. Precisely how did they live? What were their ties to the natural world around them? In this study, based upon some six years of intensive archeological and geological research at Labras Lake in St. Clair County, Illinois, Richard W. Yerkes interprets a wealth of important new data in a stimulating and original fashion. With a fine-tuned control of the data, Yerkes challenges prevailing theories based on simple classifications of stone tools according to shape or on simple models of diffuse and focal economies. He views environment as a dynamic factor in economic and cultural life, rather than as merely a backdrop to it. Using incident light microscopy, he examines wear patterns on stone tools to determine what activities were performed during each period the site was inhabited—the Late Archaic, the Late Woodland, and the Mississippian. As he documents environmental change at Labras Lake, he analyzes plant and animal remains in context to explore diet and seasonal patterns of subsistence and settlement. The result is a more accurate and detailed picture than ever before what prehistoric life on the Mississippi floodplain was like. Yerkes shows how to assess the duration and size of occupations and how to determine where and when true permanent settlements arose. What others call "sedentary encampments" he reveals as sequences of small residental occupations for a narrow range of activities during shorter, seasonal periods. His contribution to the study of the development of sedentism is potentially far-reaching and will interest many North American anthropologists and archeologists.