This National Forest campground is directly across the 2-lane "highway" from Custer State Park, a beautiful park with several campgrounds, vintage lodges and cabins, lovely small lakes and plenty of opportunities to see wildlife (we saw bison -- of course! -- mountain goats, wild burros, deer, and turtles).  Bismarck Lake campground is small and quiet (except for generators until 10 pm --- grrrr!) with several really beautiful sites.  There is water and the vault toilets were super clean.  We were in Site 2, one of the worst (right next to the campground road with a slope down to the picnic table/fire pit), but it was still pretty nice.  The best sites are 4, 5 and 8 which all have lake views; 6 and 7 which are next to each other on a large rock outcrop, with graded sites for tents -- they are close together though; and 21 (20 on one map) which is in a meadow all by itself (the Recreation.gov and Forest Service maps of the campground have numbered the sites differently; both show site 8 on the wrong side of the road).  There is a good graded path down to the lake, a sweet bridge over the dammed part of it, and a boardwalk around one side of it.  The lake is gorgeous -- so beautiful at dusk.  Across the highway in Custer State Park is Stockade Lake, which has its own little beach and a playground.  Stockade Lake South Campground has free showers (you have to pay a $20-per-car one-time fee  to get into and use any/all the facilities in Custer State Park -- totally worth it as there is so much to do!).  Mt. Rushmore is just over a half-hour away; the Badlands are about 1 1/2 hours.  Custer is a pretty cute little town (as opposed to Keystone, near Mt. Rushmore, which is a true tourist trap) with a good little grocery store (Lynn's DakotaMart) and an Ace Hardware, as well as a GREAT pie shop/bakery/cafe.