Book excerpt: This historical work chronicles the lives, adventures, and discoveries of America's great explorer/naturalists--Lewis & Clark, Martha Maxwell, John James Audubon, John Muir, William Gambel, Thomas Say, Robert Kennicott and John Townsend. Regardless of the formidable obstacles and travails, these naturalist-explorers provided an invaluable scientific foundation as to how the plants, animals, and environment of the American West coexist. From identifying new species to discovering prehistoric fossils, this book celebrates these intrepid trailblazers who boldly navigated and documented the untrammeled, awe-inspiring frontier west of the Mississippi.