Foreword, Edward O. Wilson. Preface. Contributors. Participating Institutions. Acknowledgements. 1. Biodiversity: Our Precious Heritage, Jonathan S. Adams, Bruce A. Stein, and Lynn S. Kutner. 2. Discovering Life in America: Tools and Techniques of Biodiversity Inventory, Bruce A. Stein and Frank W. Davis. 3. A Remarkable Array: Species Diversity in the United States, Bruce A. Stein et al. 4. Conservation Status of U.S. Species, Lawrence L. Master et al. 5. State of the States: Geographic Patterns of Diversity, Rarity, and Endemism, Bruce A. Stein et al. 6. The Geography of Imperilment: Targeting Conservation towards Critical Biodiversity Areas, Stephen J. Chaplin et al. 7. More than the Sum of the Parts: Diversity and Status of Ecological Systems, Mark T. Bryer et al. 8. Leading Threats to U.S. Biodiversity: What's Threatening Imperiled Species, David S. Wilcove et al. 9. Strategies for Biodiversity Protection, Michael J. Bean. 10. Owning Up to Our Responsibilities: Who Owns Lands Important for Biodiversity?, Craig R. Groves et al. 11. Safeguarding Our Precious Heritage, Mark L. Shaffer and Bruce A. Stein. Appendix A: Extinct and missing species of the United States. Appendix B: State Diversity, Endemism, and Rarity. Appendix C: Kuchler Potential Natural Vegetation Types. Appendix D: Principal Sources for the Natural Heritage Central Databases. Literature Cited.