EVENT | Apr 15 - 18, 2021 Mark Twain Cave Rally 15 - 18 Apr Mark Twain Cave Campground 300 Cave Hollow Rd Hannibal, MO, 63401 | Get Directions W Mark Twain Cave Enjoy historic Mark Twain Cave and scenic Hannibal on the Mississippi River. Event Contact Joe Hauser, Club President camperqueen2000@yahoo.com Share Event The Mark Twain Cave Complex boasts America’s oldest and newest show caves! Mark Twain Cave is Missouri’s first show cave. The first organized guided tour was in 1886. Mark Twain Cave became a National Natural Landmark in 1972.