Just off the paved loop around the rest area. Keep en eye out for muggles!
Regular size cache with one compartment for tradable items and one for geoswag. We stop at this rest area on our way to the cities from Grand Rapids. I was surprised it didn't have a geocache, but now it does. Watch out for muggles as you venture out for this cache. Rehide as well or better than you found it.
http://en.m.wikipedia.org/wiki/Rum_River