You covered state parks and the national park service nicely. Michigan also has land designated as federal wilderness areas. Here's a link to the USFS Wilderness Area page that covers the Sylvania Wilderness, McCormick Wilderness, and Sturgeon River Gorge Wilderness areas. Supposedly, this area is the largest roadless area in the state.
"Got tight last night on absinthe and did knife tricks. Great success shooting the knife into the piano. The woodworms are so bad and eat hell out of all furniture that you can always claim the woodworms did it."