When you are researching a legal topic for the first time, a subject specific research guide is a good place to start. Listed are several legal research guides from other law schools.
University of Tulsa College of Law Guides- Native American Law Web Sites
Georgetown University Law Center Guide- Native American Law Research Guide
University of Oklahoma Law Library Guide- Native American Law Research
The guides below are focused on Native American resources in General
Michigan State University LibGuide- Native American Studies
Gallagher Law Library- Indian & Tribal Law
This map and several other demographic maps are available from the United States Census Bureau.
Source: https://www2.census.gov/geo/maps/DC2020/AIANWall2020/2020_AIAN_US.pdf
Source: Oklahoma Historical Society