Native American Pastel - Nature Scene circa 1920-?

My great grandfather was a constitutional scholar and lawyer who argued many cases before the US Supreme Court and lower courts, sometimes on behalf of indigent clients. Being a country lawyer he would often take items in trade or barter for his services. One such item was painting a painting by an early African American surrealist that was valued in the six figure range upon it's donation to Howard University in the late 80's.

Another piece of artwork has been passed three generations to me and has been in a box for decades. It needs to find a suitable home where it can be appreciated. The family "oral history" tells a story of a Native American tribe hiring my great grandfather to represent them in dealings. He was paid with a pastel landscape, whose value then must of been commensurate with his services rendered. He practiced law in Manassas, Virginia from 1920's til the late 1950's. Any help in identifying the artist, tribe or era the painting would of been done in would be appreciated. Ultimately the artwork needs to be where it can be appreciated either an individual or a relevant institution. I can send a picture of the artwork, frame and signature upon request.