"In one very real sense," David Lavender writes, "the story of the Oregon Trail begins with Columbus." This opening suggests the panoramic sweep of his history of that famous trail. In chiseled, colorful prose, Lavender illustrates the "westward vision" that impelled the early explorers of the American interior looking for a northwest passage and send fur trappers into the region charted by Lewis and Clark. For the emigrants following the trappers'...