Finding the Orphan Boy/Cooper Cabin
The Orphan Boy is a special place. First of all, if you haven't been there before, and you want to go in winter, you could be in for a significant challenge to find it. The trail will be almost completely obliterated by snow, and emerging at the correct spot after crossing down through the ravine is difficult. I tried to go there in winter three times, with no success, before going in the summer, when it was much easier to find. Once you have been there, winter route finding is a lot easier.
The routes are marked on the map below. The trail up Keller Mountain starts from the Gore Range Trail. The map shows 2 approaches: from Rock Creek via the Rock Creek trail (yellow), and from Rock Creek via the old Wagon Road (blue), which leaves directly out the back of the parking lot. These approaches econverge at the northern edge of a large, aspen-rimmed meadow/bowl that the Gore Range Trail skirts.
Head up the trail - it starts with a hard, steep pull and continues up, up, up. Once on the ridge, you can begin to see up North Rock Creek Valley (~10,600'), ending with a nice rest spot (and downed log) with a view of the North Rock Creek headwall and summit of Mt.Keller (12,800'). Continuing on, you will pass a man-made ditch on your left that heads straight down the fall line. You are now directly above the Boss Mine tailings (the ditch was used to snake logs down to the mine, and it was a favored route by the Coopers). Continue on a short distance to the fork in the trail (in 2017, a tree fell right at the fork). The left fork goes up to timberline, the right fork goes to the Orphan Boy cabin. This trail gently climbs about 200', curving around to the left, and ends at the remains of a log cache (about 4' high).
You are now on the edge of the ravine, and will descend steeply nearly 400' through a stunning virgin spruce forest, crossing a small stream and an avalanche track - a big slide occured in ~2014, and it is easiest to work your way down along side of it until you can cross over. Then go up the hill a short distance and you will encounter the trail. Go right and soon you will arrive at the cabin.
The cabin is also accessible by hiking up Rock Creek to the Boss Mine, and taking the trail at the top of the tailings, up to the ridge. Another route is from Boulder Creek, and while the route is beautiful in its remote wildness, it is a steep and trailless slog.