"John Wesley Powell: explorer, writer, geologist, anthropologist, land planner, bureaucrat. Which one do we focus on?" This is the question author James M. Aton poses at the beginning of his biography of Powell, though he soon decides that it is impossible to ignore any facet of Powell's life. Powell was a polymath, one whose "divergent interests resemble one of those braided streambeds in his beloved canyon country, branching out in many directions,...