These are directions for Custers Gulch another campground in the area near Custer State Park. Hope this helps.
How to get here from I-90:
Take Exit 61 go about 8 miles.
Turn left on 16 at top of hill next to waterslide park. Go to Hill City.
At Hill City the Hwy becomes 16 West and 385 South stay on it to Custer.
In Custer turn left (east) at stop light (on 16A) go about 3 miles.
Custer's Gulch Campground on right (south) side of Highway.
If you get to Custer State Park entrance, you have gone too far and there is room to turn around at the entrance.