Rock River Falls, photo by Shadows in Reflection.

The Rock River Falls entry on the fantastic waterfall info site Go Waterfalling says:

This wild waterfall is hidden in the Rock River Wilderness Area north of Chatham. Reaching it will require you to drive down some old logging roads and hike a mile or two along some ill defined trails, but if you are looking for a good waterfall adventure it is worth it.

Trails.com has a map to Rock River Falls and Hunt’s UP Guide notes that the falls are in the Rock River Canyon Wilderness, which has “no signs, no waste containers, no planned improvements” but does boast a 150′ deep canyon and the Eben Ice Caves. You can read a lot more about Rock River Canyon Wilderness right here.

See it bigger in Michael’s Waterfalls slideshow (view the set).