If you are seeing Mount Rushmore and Crazy Horse it is just a little further south to the Mammoth Site in Hot Springs, which has several inexpensive hotels ( Stay USA was my choice). This a real, on-going dig with a building built over the 150 foot site that is a 65 feet deep excavation, where you see real bones in place as they are found. So far they have found 61 mamoths which fell into a water filled sink hole. Guides are knowledgeable, exhibits are good and the gift shop has neat stuff that is not over priced. Hot Springs is less crowded than near Mount Rushmore.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.