In the 1880's, grain was ground in mills, and was put into the mills using a millhopper, a large funnel on the top of the mill. When this site was discovered, fossilized bones and teeth were found, leading to a superstition that this was the milhopper to feed the devil. Hence, the name.
Scientists have learned a lot from the Millhopper, not only about the geological makeup of Florida, but also about ancient life from the fossilized remains and plants found in it. The site was purchased by the State of Florida and became a state park in 1974.
This railroad tie is all that's visible now of the trail built in the 1930's by the Conservation Corps. The main disadvantage was that the trail caused excess erosion on the side of the sinkhole. The current trail is elevated, minimizing the impact.
The Millhopper has its own mini-ecosystem, due to its shape retaining a fairly constant temperature, kind of like a cave. Luscious ferns and mosses are found all around the inside of the sink, feeding off the mineral rich water and rock. Bottom of the sink.
This is a Needle Palm, which is normally found in areas further south in moist, dark areas. Here in northern Florida, they are only found in deep crevices and ravines, like this sinkhole.