This dissertation examines the colonial history of anthropology. Specifically, I examine the history of an anthropological theory known as linguistic relativity. The theory posited that the unconscious structure of language was linked to patterns of thought and culture, creating distinct worldviews among different language communities. With intellectual roots dating back to the Enlightenment, linguistic relativity developed into a modern science in the United States in the early-twentieth century. My study focuses on how this iteration of the theory was linked to settler-colonial institutions and state power. I also focus on the subaltern experience of North American Indigenous communities impacted by this history of anthropology. On this front, I emphasize the politics of the American Indian self-determination movement. By bringing the history of anthropology, U.S. empire, and American Indian politics into a unified historical narrative, my project reveals a nuanced story about the history of science. My thesis is that, in the United States, the theory of linguistic relativity was instrumentalized in the political project of settler colonialism.