My dissertation is about forms of locally-based piety, especially religious devotion within the population of eighteenth-century Spanish descendants in Monterrey, Mexico. This study takes the reader through the structure of the colonial last will and testament, identifying its principle parts, analyzing its formulaic language, and discerning ways to hear the voice of its testator. Reineros, or colonial residents of Monterrey, entrusted scribes to write their wills in order to care for their souls in the afterlife and bequeath their possessions to family members, friends, and the church. Testators demonstrate their piety by issuing directives concerning their burials and funerals and making pious bequests to benefit church adornment, chapels, charities, and devotions to images. I identify trends in piety over time and offer a proposal for understanding the context of these variations. I propose that Monterrey’s distance from other urban centers made it a distinctive frontier town in northeast Mexico, where a baroque-infused piety dominated local religious practices even after the creation of the diocese in 1777. However, I demonstrate that late eighteenth-century and early nineteenth-century testators, although still concerned for their individual souls, requested fewer masses for the dead to benefit their souls and the souls of others, made fewer charitable gifts, and disregarded showy funerals for the sake of humility. What emerges, then, is a blend of baroque practices and pious reforms. “En el Nombre de Dios” is a case study about the staying power of traditions and the enduring flexibility of religion.