Standing at the Mouth of Cavern, Longhorn Cavern State Park, c. 1935
Over the course of several million years, water seepage formed holes in the limestone beds under what is now Burnet County. The seepage developed into an underground river, and the holes gradually became a series of connected chambers extending over eleven miles in length. Along with the landscape work on the surface, the CCC built levees and drainage holes to control flooding, cleared at least 1½ miles of the cavern, and installed lighting.
NARA Denver