South Dakota, USA
They say the Great Plains were covered by a prehistoric sea. In Badlands National Park, you can see Pierre shale, the sedimentary rock that used to be at the bottom of that sea.
Then at the turn of the twentieth century, these places were the sites of the final battles between war-bonneted war chiefs and F-Troop like U.S. Cavalry.
These photos show the Badlands rock, depending on the level of the sun.
To think I may have missed this if I had not looked at the map on time! The Badlands National Park is near Wall, South Dakota.
Buy it. Read it. (Or listen to it.) Let me know what you think. –TMLL