This cache is located on the Black Hills National Forest about 100 feet from the boundary with Custer State Park. If you look east in the rocks above the cache, you will see a red post that marks the boundary. The cache cannot be placed in Custer State Park since it would violate park rules prohibiting physical caches. Rules for caches in South Dakota parks vary among parks. The last time I checked, all parks allowing caches required specific permission for each cache. It is best to check each time I plan a cache.
It is important to know where the ownership boundaries are when placing any cache. Once you know the landowner, you can ask permission from a private landowner or verify you are following established policy for public land. Some public land requires specific permission, so it is imperative to find the applicable requirements.
The Black Hills National Forest has about 95% of its boundary surveyed and marked on the ground. Custer State Park also has its boundaries marked on the ground. In some places the two boundary lines are 15 to 20 feet apart. One instance of that can be seen on the south side of the Forest Service campground at Bismarck Lake near site 14 which is partially on Custer State Park land.