Interethnic marriage represents a major trend in the demographic history of American Indians. While the majority of these unions involved Indian women and Caucasian men, a sizeable number occurred between Indians and African Americans. The children of these bicultural marriages were "mixed bloods" who in turn typically married non-Indians or other mixed bloods. Using data from the 1910 Census on American Indians in the United States and Alaska, this article explores why American Indians with African ancestry enjoyed high fertility. Differential rates of fertility among American Indians in the past were due to a number of underlying genetic, cultural, and environmental factors. By identifying these factors, the paradox of why Indian women with African heritage did so well in terms of fertility largely disappears. African admixture, however, greatly complicates Indian social identity.