We visited Maquoketa Caves State Park today for the first time and it definitely lived up to the hype. I heard you should arrive by 10 am because parking fills quickly and that's almost exactly what time we pulled in. We got the last spot in the closest lot, however those restrooms are closed so we had to trek to the upper parking lot anyway and that lot was huge and almost empty.
The Iowa DNR map is hard to follow, so I recommend paying 99 cents for the Iowa Parklands' version. In fact, they sell his bandana map at the Friends of the Maquoketa Caves concession stand by the main parking lot, which is open on the weekends. They also sell popsicles, which my kiddos appreciated on such a hot day. If you forget your headlamps, they have those for sale too.
We really enjoyed our visit and look forward to returning. I had trouble deciding where to stay due to Maquoketa Caves' somewhat remote location and we ended up in Anamosa, which I wouldn't recommend. Next time, we plan to stay in Dubuque which is where we headed for dinner after our cave hike.