Thanks for posting this. The family and I were on a trip from Stevenson, AL to Idlywild, CA and traveled down that highway in ‘91. We saw a roadside historical marker and turned off to view one of these. However, I couldn’t remember exactly what I had read prior, I think it had been in National Geographic, and so I have wondered off and on about the glyphs over the years.
Thanks for filling in detail. I was beginning to think that I had romantized what we viewed that day.
See my #9.
That is one reason we try to avoid Interstates when traveling, except in mostly familiar territory. Might be quicker, but you miss too much that you may never get back again to see.