Civil War historiography has been well served by the recent proliferation of borderland studies. This burgeoning corner of the conflict’s literature has added nuance to our understanding of emancipation, the war in Appalachia, the Confederate diaspora, the Native American experience, and the war’s transnational dimensions. Civil War in the Southwest Borderlands by Andrew E. Masich is an accessible and well-researched addition to the literature. In this sweeping, largely narrative history, Masich argues “that cultural groups fought civil wars in the Southwest Borderlands concurrent with and connected to the American Civil War and that such wars often occur when two or more ethnically or culturally distinct peoples occupy the same space and v...