“Race,” as a concept denoting a fundamental division of humanity and usually encompassing cultural as well as physical traits, was crucial in early America. It provided the foundation for the colonization of Native land, the enslavement of American Indians and Africans, and a common identity among socially unequal and ethnically diverse Europeans. Longstanding ideas and prejudices merged with aims to control land and labor, a dynamic reinforced by ongoing observation and theorization of non-European peoples. Although before colonization, neither American Indians, nor Africans, nor Europeans considered themselves unified “races,” Europeans endowed racial distinctions with legal force and philosophical and scientific legitimacy, while Natives appropriated categories of “red” and “Indian,” and slaves and freed people embraced those of “African” and “colored,” to imagine more expansive identities and mobilize more successful resistance to Euro-American societies. The origin, scope, and significance of “racial” difference were questions of considerable transatlantic debate in the age of Enlightenment and they acquired particular political importance in the newly independent United States. Since the beginning of European exploration in the 15th century, voyagers called attention to the peoples they encountered, but European, American Indian, and African “races” did not exist before colonization of the so-called New World. Categories of “Christian” and “heathen” were initially most prominent, though observations also encompassed appearance, gender roles, strength, material culture, subsistence, and language. As economic interests deepened and colonies grew more powerful, classifications distinguished Europeans from “Negroes” or “Indians,” but at no point in the history of early America was there a consensus that “race” denoted bodily traits only. Rather, it was a heterogeneous compound of physical, intellectual, and moral characteristics passed on from one generation to another. While Europeans assigned blackness and African descent priority in codifying slavery, skin color was secondary to broad dismissals of the value of “savage” societies, beliefs, and behaviors in providing a legal foundation for dispossession. “Race” originally denoted a lineage, such as a noble family or a domesticated breed, and concerns over purity of blood persisted as 18th-century Europeans applied the term—which dodged the controversial issue of whether different human groups constituted “varieties” or “species”—to describe a roughly continental distribution of peoples. Drawing upon the frameworks of scripture, natural and moral philosophy, and natural history, scholars endlessly debated whether different races shared a common ancestry, whether traits were fixed or susceptible to environmentally produced change, and whether languages or the body provided the best means to trace descent. Racial theorization boomed in the U.S. early republic, as some citizens found dispossession and slavery incompatible with natural-rights ideals, while others reconciled any potential contradictions through assurances that “race” was rooted in nature.