The Western Black Hills are snowmobile country. Drive West on US 85 in winter and you'll notice numerous snowmobile crossing signs, as well as circles and figure-eights in roadside meadows. There's also some lesser known opportunities for non-motorized winter sports.
Snowshoeing is heating up in the Pacific Northwest, but not necessarily in the Black Hills — which should be fine you if it's snowy solitude you're after. Cross-country skiiers — who often coexists with shoers — are somewhat more prevalent.
The Beaver Creek Ski System is one of the Hills' best kept secrets for self-powered winter sportsfolk.
Getting there requires leaving our beloved South Dakota, but most of the trails thankfully cross back over the Wyoming border. (Your winter sports correspondent shoed for the border as if trailed by twenty hounds.) The trailhead is about a half mile past the endearingly-named Mallo Camp (an off-and-on snowmobile resort), on Mallo Road. You might imagine an amiable Stay Puft man-of-the-forest — who has traded in his sailor get-up for something more like a Scout's neckerchief — and treads lightly through this marshmallow world serving as a woodland medic to injured animals.
You can park where the road closes to wheeled traffic, then walk another tenth of a mile, where the Porcupine Trailhead begins on the East side of the road. You'll see a "no snowmobiles" sign. From there you can design your own route across interconnected trails. The trails are well-marked with blue-diamond blazes, and exceptionally easy to follow most of the time, though it won't hurt to have a GPS on occasion. There are also markers and trail maps at the intersections of the numbered trails.
The trails meander through rolling spruce, ponderosa pine and aspen forest, with an altogether different mystique than the needly granite heart of the Eastern Hills. The highest peak on the trail system is Highland Ridge on the Highland trail, offering seldom-seen views of the Western Hills from 6,704 feet. The Highland Ridge vista is about 3.75 miles from the Porcupine Trailhead.
The trails are not groomed. Shoer etiquette simply means not walking over ski tracks where they exist. There's a good chance you'll be breaking trail and won't see a soul.