The first is that of Wind Cave from western South Dakota. This one is unusual and that there are over 135 miles of mapped and explored caves in the system, making it one of the longest in the world. It sits beneath the largest natural grass prairie in the United States.
The second is Marble Cave, located in Missouri. This one is unique because these drawings were done in the late 1800s and there's a book about the cave available via the Gutenberg project.
Geomorph done in 1894 by Fred Prince
I think this next map is particularly evocative simply because it shows the massive amount of space in the Wind Cave system in South Dakota.
This one isn't so evocative but is perhaps more useful as a regular survey/map of the Wind Cave system in South Dakota.