Pinckny State Recreation Area (Michigan)
Mountain bikers will know it as Potawatomi, but the Pinckny State Recreation area has more to offer than just singletrack (though that would have been more than enough). The 24-ish miles of trail includes tech challenges and sustained climbs, while the Pinckny campgroundfeatures running water, electricity, and “modern restrooms.”
I got a chance to camp and bike at Switchgrass last summer and was blown away at the quality of both the singletrack and the campground. The trails are officially world-class with a recent IMBA Epic designation, and the campground facilities include showers, flush toilets… and very few crowds during the week. Plus, you’re on a lake, which makes for a refreshing place to cool off after a hot ride!