From Wikipedia (and I promise to make a donation this week as I use this source a whole lot).
In the previous post, I mentioned the Mitchell Cave. I don't remember seeing it or knowing about it back when we went through there in 2006, but at one time it was a privately-owned tourist attraction and now operated by the state. Perhaps I'll go there the next time through.
It is now called Mitchell's Caverns in the California State Mitchell Cavern Natural Preserve and is located at the end of Essex Road (the one Jack Mitchell built) near I-40 (The Needles Expressway, I didn't know that) in San Bernardino County, California.
Jack Mitchell owned and operated the site from 1934 to 1954 as it served as a tourist attraction and rest stop for travelers along the old Route 66. He also had mining rights in the area and dug several prospect holes and tunnels, some of which still exist.
It became a state recreation area in 1956. The surrounding area is now part of the National Park Service's Mojave Desert unit, but the caverns are still operated by the state. Tours can be arranged.
Something to See Out in the Desert. --RoadDog