Located just north of the town of Custer, Buckhorn Mountain (6,330 ft) is accessible and little-hiked at once. No established trails exist, but following the topography makes it difficult to get lost, and bushwhacking through the open forest (BHNF land) makes for a moderately challenging hike with excellent views of Crazy Horse Monument and the southern side of the Black Hills Core region as a reward.
Two routes (from opposite sides of the mountain) provide access to Buckhorn Mountain, and both are less than 5 minutes driving time from Custer.
The western approach is reached via the Mickelson Trail trail head just North of Custer on 385. Leave the trail and proceed directly up the western slope of the Mountain, or you can meander through huge granite canyons which slope gently upwards to form the massive shoulders of the mountain. From the top of these, you can work your way South-East to the main peak, or enjoy the views from any of the smaller rocky sub-peaks.
From the east, take 16A E out of Custer, turning N onto 89. Take Fire Road 362 (on the left, 1 mile N of the junction of 16A & 89). Parking off of the Fire Road, hike due East into the Black Hills Nation Forest, straight up the eastern shoulder of the mountain. Be careful to avoid going off the road north or south, as there are private homes to either side in the woods along the road. Once you are hiking uphill, you can go either left or right of the center ridge that crops up, but the right-side (North) route is recommended - the southern approach forces steep detours as massive rocks block your way. Follow alongside the ridge line bearing uphill. There is a false summit, which offers a view of the real thing not far ahead. Just follow the ridge-line down and back up again, and keep heading west to the summit. A cliff at the top offers great views of Crazy Horse's face to the North.
Whichever route you choose, there are plenty of great opportunities to explore the smaller sub-peaks, valleys, and canyons along the sides of Buckhorn. (YDS Class 2)