This dissertation traces the material, relational, and affective constructions of racial skull collections from the late eighteenth century to today. In charting the development of “cranial race science” from physiognomic discourses to the localization of racial difference in the braincase, this dissertation asks: Why did skulls become central in emergent late European Enlightenment racial science? Why did a handful of colonial and imperial knowledge production centers become this science’s foundational sites? How did contests over racial politics and scientific legitimation overdetermine skull measurements? Would human skull collections amassed for racial science exist had the violence that produced them been visible, or had identities, names, and histories not been severed from human remains? What kinds of discretion, secrecy, and concealment were deployed to normalize the collection of human skulls against the wishes of the deceased, their kin, and broader publics? What has caused shifts in the perceived scientific value and ethical status of historic human cranial collections in museums? This dissertation draws on archives of racial science from ca. 1768–1851, especially in the United States, Germany, the Netherlands, and on close readings of primary texts, and on museum-based research across the U.S. and Europe. The first chapters follow the measurement of “cranial capacity” and how it became the key measurement through which the scientific legitimacy of nascent phrenology and debate about the abolition of slavery were articulated. Both the mass collection and measurement of human skulls were first deployed by white scientists arguing for human unity or abolition, but these practices proliferated among those arguing the opposite. Critically reading the documentation of cranial collections in the context of anatomy riots into the mid-nineteenth century shows that collectors strategically depersonalized human remains, withholding names and identifying information from published records, revealing biases about whose bodies could be made into spectacles of violence, and whose could not. Tracing the afterlives of the Morton collection in Philadelphia suggests that racial cranial collections have always been ethically contested, that they were created by, for, and within asymmetric, racialized power structures, and have remained intact only insofar as those structures predominate.