Yes!!!   You're terrific!!!

The single car ferry crosses the Green River on the north entrance to Mammoth Cave National Park. No RVs are allowed on this ferry. For more information on the ferry, Green River or the park click here

We were there on April 5 & 6 in 1989. Here is what I wrote in my diary.

We left General Butler State Park for the drive to Mammoth Cave. It was only a 150 mile drive. It was cloudy but it was a pretty drive. The campground at the park is nice and nearly empty. There are some tents which surprised us since it is so cold---yukku cold. We got our mail right away. That works great. Also got tickets for the 1/2 day tour tomorrow (Thursday).

Sun was shining in the morning so we biked, but it was too cold. So we hiked 2 miles to the Green River. It was a stiff walk. It is strange to see this single car ferry that goes across the narrow river. Later we did the historic tour in the cave which was 4 1/2 hours of strenuous walking. We met a deaf man who lives in his van most of the winter and has been doing this for 5 years. Neat man. He told us to be sure to go to Yosemite National Park and spend a week. I have never heard of it so we will look it up. It is in northern California. Anyway he is a great grandfather. 

Friday Morning
We nearly froze; it felt like we were tenting. We had to sleep bundled up. There's no electricity in the campground (national parks don't normally provide such) and our battery was low when the furnace was on. It was okay but like tenting only more comfortable and unlike tenting, we did turn our furnace on in the morning and was able to warm up. We are leaving. Got to find someplace warmer. Heading further south --- to Nashville.