I remember reading a story about the rock wall of rockwall texas and how it corralates with an indian legend. Ill try to find it but it goes something like this.

A northern indian tribe begins to concor land southward. They keep moving further and further south, slaughtering tribes along the way.

When theyre met by an impenetrable wall, and an indian tribe they described as "moon people" because their skin and hair was fair and light.

They then, of course, slaughtered the moon people and settled at the wall because they could go no further.