Indian Affairs: Laws and Treaties by Charles J. Kappler, who was clerk to the US Senate Committee on Indian Affairs, is a standard source for full-text treaties and agreements made by the US government with various Indian tribes and bands from 1782-1883. Volume 2 contains full-text treaties. Links below are from GovInfo, an OA US government site; the pdf's of these massive volume can be very slow to load. (Scans of Kappler's content can be found in many other sources including HeinOnline, where scans are faster to load and easier to search.) The library also has print copies of Indian Affairs: Laws & Treaties at E94 U6 1904, all volumes.