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...