The story of the threatened coastal California gnatcatcher is a parable for understanding the larger ongoing struggle to conserve biodiversity in regions confronted with intensifying urban development. Because this gnatcatcher depends on vanishing coastal sage scrub in Southern California, it has been regarded as a flagship species for biodiversity protection since the early 1990s. But the uncertainty of the gnatcatcher’s taxonomic classification-and whether it can be counted as a listable unit under the Endangered Species Act-has provoked contentious debate among activists, scientists, urban developers, and policy makers. Synthesizing insights from ecology, environmental history, public policy analysis, and urban planning as she tracks these debates over the course of the past twenty-five years, Audrey L. Mayer presents an ultimately optimistic take on the importance of much-neglected regional conservation planning strategies to create sustainable urban landscapes that benefit humans and wildlife alike.