The new model of policy design theory frames the discussion regarding the frequently analyzed Endangered Species Act (ESA) in this historical perspective. Since the 1970s, the Endangered Species Act (ESA), by virtue of its regulatory impact, has been a frequent subject of policy analysis. In this comprehensive history and critique of the ESA, Brian Czech and Paul R. Krausman incorporate the new model of policy design theory to frame a larger discussion about conservation biology and American democracy. Czech and Krausman provide a historical background of endangered species policy that integrates natural history, socioeconomic trends, political movements, and professional developments. Outlining the controversies surrounding the ESA, they find a connection between challenges to species conservation and challenges to democracy. After an assessment of ESA analyses that have been performed from traditional perspectives, they engage policy design theory to review the structural logic of the ESA, analyzing each clause of the legislation for its application of the fundamental elements of democracy. To address the technical legitimacy of ESA, they propose two new genetic considerations—functional genome size and molecular clock speed—to supplement phylogenetic distinctiveness as criteria with which to prioritize species for conservation. Next, they systematically describe the socioeconomic context of ESA by assessing and classifying the causes of species endangerment. A hybrid of policy analysis and ecological assessment, The Endangered Species Act: History, Conservation Biology, and Public Policy will appeal to scholars and students in the fields of natural resource policy and law, conservation biology, political science, wildlife ecology, and environmental history, and to professionals at agencies involved in wildlife conservation.