Oklahoma has a large Indian population...but no Indian reservations.
The economic (and cultural) lot of the non-reservation Indian is far, far ahead of the reservation Indian.
You’re forgetting the Osage Nation contiguous with Osage County. There’s still counties left that are remnants of the original nations: Cherokee, Choctaw, Creek, Kiowa, Muskogee, Osage, Ottawa, Pawnee, Pottawatomie, Seminole.