RAND Californiaprovides easy access to statistics about California; some databases cover the entire United States. (CSUN subscription; not available to all users) Suggestion: Statistics Summary, ... by race (U.S. State and County Population Statistics By Race and/or Age)
This site contains the fully searchable digitized text of all seven volumes from the original 1903-04 U.S Government Printing Office publication. Based at Oklahoma State University Library, these volumes contain U.S. government treaties with Native Americans from 1871-1970 as well as U.S. laws and executive orders. Information can be accessed from the table of contents, through the index of each volume, or by keyword search.
Native American Constitution and Law Digitization Project.
Housed at the University of Oklahoma Law Library, this project is a cooperative effort between the University of Oklahoma Law Center, the National Indian Law Library, and Native American tribes. The site provides access to constitutions, tribal codes, a digitized version of the Handbook of Federal Indian Law (1941) by Felix S. Cohen, documents of Indian land cessions, Indian Reorganization Act Era Constitutions and Charters, and many other resources for researchers of Native American legal issues.
National Indian Law Library (National American Rights Fund)
A public law library devoted to federal Indian and tribal law. It collects all resources specializing in legal practice materials which are essential for practitioners of Indian law, including books, pamphlets, federal government documents, state government documents, scholarly reports, journal articles, newspaper articles, student reports, and law reviews. NILL digital collection contains full text of primary and secondary resources.
Native American Constitution and Law Digitization Project. 
National Indian Law Library (National American Rights Fund)