Karl Jacoby is a professor of history at Columbia University. His research considers how power relations within human society are reinforced, complicated, and, at times, effaced through interactions with the natural world, especially with regard to the history of U.S. expansion. His first book, Crimes against Nature: Poachers, Squatters, Thieves, and the Hidden History of American Conservation (2001), examines the ways in which the United States sought to exert new forms of control over nature through the conservation movement. His second book, Shadows at Dawn: A Borderlands Massacre and the Violence of History (2008), focuses on the ways the tremendous violence toward American Indians that accompanied the "frontier" has been remembered and forgotten in the intervening years. His latest book, The Strange Career of William Ellis: The Texas Slave Who Became a Mexican Millionaire (2016)—winner of the OAH Ray Allen Billington Prize—analyzes race and slavery along the U.S.-Mexico border through the life story of a one-time slave who made many journeys across the race line and the border line.