The Pinnacle Falls entry at GoWaterfalling.com explains that:
Pinnacle Falls is located on a wild stretch of the Yellow Dog River, roughly 8 miles south west of Big Bay. The Yellow Dog has carved out an impressive gorge that must be around 200 feet deep. The falls is about 25 feet high, and is a steep cascade like many of the falls in the area. The falls is named for the large pinnacle of rock on the right side of the falls.
This was I think the most remote Michigan waterfall I have been to. The only directions we had was an article written in 2006 from some guy who found it on his mountain bike. He included the GPS way-points but when we reached it there was no falls or trail around. We went down one last two-track with the jeep after trying for a couple of hours, and finally found the trail to the falls. It was about a 25 minute hike. The Yellow Dog has carved out an impressive gorge back there. This would be a great place to pack in and pitch a a tent for a night or two. Very beautiful Waterfall. The photo doesn’t do this area justice.
That’s a pretty deep hole right below the falls, I couldn’t resist stripping down and swimming for awhile. :)
Many (many) more waterfalls on Michigan in Pictures.