I live a few miles from the Morton Salt Plant at Grand Saline Salt Dome. They have mined down to 750’ and say they can continue for 20,000 years. And this is just one salt dome in Texas. There are hundreds from Texas to Mississippi.
Mining in Texas has a long and storied past.
I may do a post on this enormous salt mine. Local newspapers occasionally do stories on it, so I should be able to get material.