It's a debate as old as the county and city named after it. In Rockwall, there's an actual rock wall, that geologists and locals have long been at odds over.
It's not far from David Canup's front door.
"Terry Utley Wade, my great, great grandfather was digging a well, " David recalled.
"They kept digging down, and digging down and they hit something hard," added county judge and local historian Mark Russo. "And it's like, 'What is this?'"
"He wondered if it was just a rock or what? So he just kinda dog-legged the well over to one side and went down and he never did find the bottom of it and that's when he decided it was a wall," Canup said.
Through the years more sections of that wall have been uncovered.
"16 different outcroppings along Rockwall, Collin and Dallas county," Russo said.
Part of the wall is now on display outside of the Rockwall County Historic Foundation's museum.
Russo points out it has unique features.
"You notice each edge hits the same amount. How is that possible? Explain that too me, it's perfect and it's on both sides," he said.
The stones fit together so well, cut, it seems with great precision.
Plus they're smooth.
Russo says the wall can't be natural.
Dr. John Geissman heads the University of Texas at Dallas' department of geosciences. "When I first took a look at this, I said 'whoa,'" he recalled.
Several years ago he was part of a team that studied the wall, to determine if it's man made or an extremely rare natural formation.
His opinion? "It's a natural phenomenon, no doubt," he said.
Geissman says the stones are made up of sand-sized particles that cemented together, and over time, cracked apart and made what looks like a wall.
"Mother Nature did a really good job, in my opinion, of having those cracks spectacularly uniform in character," Geissman added.
Skeptics like Russo don't agree.
"It's easier to explain that way. Now you gotta go, 'Well, who did it? When did it happen?'"
Russo believes it was built by pre-Caddo Indians, 2 to 3,000 years ago. He says artifacts found near the wall are proof, though he'll never know for sure.
"If I was Marty McFly and I could hop in my Delorian going 88 miles an hour, we might have that answer, but that's not possible either," he joked.
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