Suffering from a case of “road fever” brought on by prolonged exposure to the journals of Lewis and Clark, Dayton Duncan has retraced the Corps of Discovery’s route from Saint Louis to the Pacific and back again four different times during the past twenty years—to say nothing of his countless additional trips to landmarks along their route. In sweltering summer heat and in temperatures 45 degrees below zero, he watched yellow moons rise and heard buffalo thunder; navigated against the Missouri River’s relentless current and stood on its surface, frozen solid overnight; canoed a dozen times through Montana’s magnificent White Cliffs (Lewis’s “seens of visionary inchantment”); and read the journals by candlelight in the expedition’s fort on the Pacific coast.