Those interested in rock art need to check out the petroglyphs in the bed of Tonk creek just upstream from Tonkawa Falls (Crawford, Texas). Normally they are out of the water only in the summer, but as dry as it has been, they may be viewable now. Short trip for those spending a day at Chrisners.
Hal, I do not recall whether the petroglyphs have been tied to any specific archeologic period. In the mid 70's, I was involved with the Central Texas Archeology Society a little, and one of our projects was cleaning and chalking the petroglyphs for a pictoral study. As of that time, I don't think anyone really knew. The rock shelters in the immediate area had occupations from paleo to pre-historic times. Based upon the name of the creek and associated waterfall, the locals contend they were made by the Tonkawa's ancestors. But most likely being pre columbian in origin, I guess no one really knows.