In late August 1998, Kim Trevathan and his dog, Jasper, set out by canoe on a long, slow trip down the 652 miles of the Tennessee River, the largest tributary of the Ohio. Trevathan wanted to experience the river in its entirety, from Knoxville's narrow, winding channel, which flows past rocky bluffs, to the wide-open waters of Kentucky Lake at its lower end. Over the course of the five-week voyage, Trevathan rediscovered the people and places that...