The Brown University Library has in its holdings a wealth of material for research on American Indians. Uncovering this material can be something of a challenge. Some formats (books, databases) are more readily discovered and user-friendly than others (microform).
See, also, Anthropology
Finding federal population data for Native Americans is not simple. From 1790 to 1940, inclusion of Native peoples in the U. S. Census was inconsistent. By 1860, Census takers were instructed to include in the Census only those Indians who were taxed. Those Native peoples who lived in traditional ways under tribal sovereignty were "untaxed," and thus not to be counted. Some traditional peoples were included in rolls compiled by the Bureau of Indian Affairs, but it is not clear that the BIA ever attempted a comprehensive census of Indian Country. The situation remained this way until the Nationality Act of 1940 extended U. S. citizenship to all persons born on U. S. soil, making all Native Americans U. S. citizens. This means that population data for native peoples cannot be accurately tracked using Census figures alone for any year prior to 1940.