This engaging and well-illustrated primer to the Upper Mississippi River presents the basic natural and human history of this magnificent waterway. Immortal River is written for the educated lay-person who would like to know more about the river's history and the forces that shape as well as threaten it today. It melds complex information from the fields of geology, ecology, geography, anthropology, and history into a readable, chronological story that spans some 500 million years of the earth's history.      Like the Mississippi itself, Immortal River often leaves the main channel to explore the river's backwaters, floodplain, and drainage basin. The book's focus is the Upper Mississippi, from Minneapolis, Minnesota, to Cairo, Illinois. But it also includes information about the river's headwaters in northern Minnesota and about the Lower Mississippi from Cairo south to the river's mouth ninety miles below New Orleans. It offers an understanding of the basic geology underlying the river's landscapes, ecology, environmental problems, and grandeur.