From the trailhead, the route is initially well signed. In the fall, unfortunately, the beginning of the trail from the parking area is really tracked out by cattle and horses, and there's a massive puddle (at least there was when I went) that you need to cross to get over to the trail (or, if you look about 100 feet to the right of this puddle, there is a small trail and a pallet bridge over the small creek that you can use to avoid the pond).
After crossing this small creek, the trail immediately starts to ascend through a rocky forest. Elk seem to like this area and can often be heard or seen near the trail along this bottom portion as the trail ascends up and into the glacial valley. After reaching the actual valley (about 1.75 miles from the trailhead), the trail becomes significantly less steep and much more manageable as the trail heads towards the lake and the head of the cirque.
There are a couple of stream crossings along this trail, and after about another 3-3.5 miles from the trailhead, the trail crosses the creek and meets up with the Shorty's Cutoff Trail, and right around this same spot are the remnants of the old steam mill that is the canyon's namesake. This section is very pretty, especially in the spring and early summer when the wildflowers are in bloom. It's also pretty in the fall as there are plenty of aspens and other deciduous trees mixed in with the conifers, that add lots of color to the area.
After passing the steam mill, about a mile later, the trail passes by Steam Mill Lake, a small glacial tarn with a moderately developed cirque headwall behind it. The trail at this point becomes braided in spots and often becomes indistinct as it gets closer to the main headwall of the canyon on the far west side below the ridge and the Doubletop Trail
. Once the trail passes Steam Mill Lake, it again becomes somewhat indistinct, and there are actually two options for getting to the ridge from here - there is another indistinct trail that switches back to the northeast and then follows the ridge along the north side of Steam Mill Canyon back to the west to get to the ridge and the Doubletop Trail
. This is the option shown on the map. The other option is to just go straight through the main basin at the head of the canyon and find a steep horse trail that switches back up the gully that leads directly to the Doubletop Trail
atop the ridge, where this trail terminates.