Drawing on rarely examined diaries and journals, Down the Great Unknown is the first book to tell the full, dramatic story of the Powell expedition. On May 24, 1869 a one-armed Civil War veteran, John Wesley Powell and a ragtag band of nine mountain men embarked on the last great quest in the American West. The Grand Canyon, not explored before, was as mysterious as Atlantis-and as perilous. The ten men set out from Green River Station, Wyoming Territory...