Borderline Americans: Racial Division and Labor War in the Arizona Borderlands

“Are you an American, or are you not?” This was the question Harry Wheeler, sheriff of Cochise County, Arizona, used to choose his targets in one of the most remarkable vigilante actions ever carried out on U.S. soil. And this is the question at the heart of Katherine Benton-Cohen’s provocative history, which ties that seemingly remote corner of the country to one of America’s central concerns: the historical creation of racial boundaries.

It was in Cochise County that the Earps and Clantons...