Snaking 2,540 miles from Montana to the Mississippi River, the Missouri is the longest waterway in the nation. Its basin—stretching 530,000 square miles—extends broadly into ten states and twenty-five Indian reservations. For millions of years the river and its tributaries meandered untamed. But that irrevocably changed with the passage of the Pick-Sloan Plan, part of the Flood Control Act of 1944. In River of Promise, River of Peril, John Thorson takes the first comprehensive look at how and why the Missouri River basin-now with six major dams and hundreds of miles of navigation canals-has become one of the most significantly altered drainage systems in the country. He also looks at the consequences. The Pick-Sloan Plan, he argues, has not fared well over time, particularly in its failure to provide an effective blueprint for regional river management. Persistent conflicts over the river, he contends, illuminate important weaknesses of federalism in dealing with regional resources, the most glaring being the exclusion of any proactive role for Indian tribal governments. To support his argument, Thorson examines the physical, demographic, and political features of the river basin; analyzes the comprehensive river development that gave birth to the Pick-Sloan Plan; reveals why the original goals of the legislature were never achieved; explores the deep-seated and continuing tensions between basin governments; and investigates how Indian tribes, the river's ecology, and federalism have been damaged as the river has been developed. He also describes the various associations created and later abandoned from the sixties to the eighties and assesses their virtues and limitations. Thorson sees in the story of the Missouri River Basin the vertical and horizontal strains of federalism-the states chafing against federally mandated and controlled projects exacerbated by the lack of constitutional guidance for handling conflicts among neighboring states and with Indian nations. Not just bent on spotlighting problems, Thorson also evaluates different approaches for improved river system management and recommends a Missouri River management institution based on environmentally sensitive policies, a strong state role, and full participation by the basin's tribal governments.