Book excerpt: America's national parks are more popular than ever, drawing record numbers of visitors every year. This special issue is a celebration of these parks, representing the best of the geographic and biological diversity of the far-flung U.S. park system. Packed with extraordinary photographs (as well as intriguing data and detailed descriptions), these pages serve not only as a guide to the parks' individual charms, but also as an appreciation of their unmatched—and fragile—natural splendor.