In this book Katherine Benton-Cohen uses the opening question, “Are you American, or are you not,” to show that what happened in Cochise County, Arizona, from 1880 to 1940, is key to how racial borders between “American” and “Mexican” took shape, hardened, and ultimately affected the entire country. A compelling social history, this study is less about a particular set of actors—the usual focus of such histories—than it is about the actions and policies of an array of protagonists unevenly mapped onto social spaces across one county.