In her book Christian Slavery: Conversion and Race in the Protestant Atlantic World, Katharine Gerbner offers a rich history of Protestant planters’ efforts to tether Christian identity to free status and European descent in the American colonies, and missionaries’ answering attempts to reconcile African and indigenous conversion with enslavement. Gerbner's concept of Protestant Supremacy names the sociopolitical function and economic utility of “religious belonging,” specifically how Christian institutional, discursive, and ritual spaces demarcated boundaries between the enslaved and their enslavers, prefiguring race in the process. In this history of Atlantic slavery, religion is not subsidiary to the punitive, legal, sexual, and economic systems that enabled the enslavement of African and indigenous peoples in the Americas. Rather, Gerbner argues that Protestant Christianity provided a metastructure for the race-based caste systems that emerged in Barbados and other British colonies in the Americas. Through an intense and extensive interrogation of correspondence, missionary accounts, and institutional records from across the Atlantic, she traces how Protestant emissaries established “Christian” as a “protoracial” term and hastened the legal and discursive codification of lineage-based American caste systems in the process. The linkage of Christian identity and nascent whiteness not only exposes the Protestant architecture of American racial logics, but also sparks nuanced questions about how African, indigenous, and creole people oriented themselves toward Protestantism in early America. In this way, Gerbner definitively situates religion at the center of ongoing conversations about racial formation in the Americas, while opening up avenues for fresh speculation and imaginative intellectual trajectories in studies of American religion and Atlantic slavery.