Custer State Park Campground, South Dakota Junction of highway # 36. North to Community of Keystone, South Dakota. North to Mount Rushmore National Mounument, South Dakota. East to communities of Hermosa, South Dakota & Rapid City, South Dakota. Black Hills National Forest - Custer State Park To City of Custer Black Hills National Forest stretches for 1.2 million acres, offering outdoor adventure like hiking, biking and camping amidst stunning scenery. Find grassy mountain meadows, towering granite peaks, deep canyons, cascading trout streams and clear, clean lakes.