Mary E. Mendoza’s monograph, Deadly Divide: How Insects, Pathogens, and People Defied the US-Mexico Border, was published by the University of North Carolina Press on April 28! When most people picture the US-Mexico border, they think of walls, fences, concrete, and wire. But in this first history of how the environment influenced physical boundary-making between the two nations, Mendoza focuses on how the natural world shaped ideas about race, gender, and security. In so doing, she unearths surprising origins of the modern-day immigration debate.