Thanks everyone for this post! I've been looking for campgrounds with availability for the next few weeks and hopefully this uncovered some new gems for us!
Booked a couple nights next weekend at Big Eau Pleine.
As for my favorites:
McLain State Park in the UP by Hancock is fantastic
And in Southeastern Wisconsin I like:
Wyalusing (busy)
and
Yellowstone State Park
We tend to find places wil lots of hiking and secluded sites (the dogs prefer it).
I also need a site with electricity (just in case the weather is hot)
We are going to the Big Eau Pleine this weekend. I only live 12 miles away, maybe I will be able to come and look you up next weekend.