Scholars have labeled Madison Grant everything from the “nation’s most influential racist” to the “greatest conservationist that ever lived.” His life illuminates early twentieth-century America as it was heading toward the American Century, and his legacy is still very much with us today, from the speeches of immigrant-bashing politicians to the international efforts to arrest climate change. This insightful biography shows how Grant worked side-by-side with figures such as Theodore Roosevelt to found the Bronx Zoo, preserve the California redwoods, and save the American bison from extinction. But Grant was also the leader of the eugenics movement in the United States. He popularized the infamous notions that the blond-haired, blue-eyed Nordics were the “master race” and that the state should eliminate members of inferior races who were of no value to the community. Grant’s behind-the-scenes machina­tions convinced Congress to enact the immigration restriction legis­lation of the 1920s, and his influence led many states to ban interracial marriage and sterilize thousands of “unworthy” citizens. Although most of the relevant archival materials on Madison Grant have mysteriously disappeared over the decades, Jonathan Spiro has devoted many years to reconstructing the hitherto concealed events of Grant’s life. His astonishing feat of detective work re­veals how the founder of the Bronx Zoo wound up writing the book that Adolf Hitler declared was his “bible.”