For a map or complete description to all the trails order Porcupine Mountains Wilderness State Park: A Backcountry Guide for Hikers, Backpackers, Campers & Winter Visitors by Jim DuFresne from the eshop:

The trailhead is marked by a giant shovel stuck in the ground and from there you depart from the north side of the parking lot to hike the trail in a clockwise direction. Within a 100 yards the trail swings sharply east (right) and descends to the Union River. You bottom out where “trap rock,” highly sought after by miners because it usually indicated copper deposits, encloses the scenic gorge on the opposite bank. The trail skirts the river and at Mile 0.2 you arrive at a bench and the location of the Union Mine’s waterwheel. Take a seat and let the waterfalls below sooth you.

The location of the first Union Mine, a collapsed tunnel, follows and at Mile 0.3 you cross South Boundary Road. The trail passes the foundation of mine’s stamp mill and then skirts a small bluff where below the Union River tumbles through more waterfalls that includes a bench overlooking one at Mile 0.5. Just down the trail you reach a junction that leads to River Trail, the winter cross-country route, and the bridge to Union River Outpost. Here Union Mine Trail swings south, following the original Nonesuch Road for a spell, to cut across to Little Union River Gorge.

From the historic road a climb of 30 steps leads to a massive hemlock where the trail swings west to follow Little Union River upstream. You past another bench with a long view of the cascades in the gorge below and then arrive at the fenced-in shaft of the Boston & North American Mining Company at Mile 0.8. The trail continues along the edge of the shady cleft, passing one cascade after another with a bench overlooking Little Union Falls near Mile 1.

In the final leg, you climb out of Little Union Gorge, cross South Boundary Road a second time and swing north to quickly arrive back at the trailhead parking area.