Hill City is about a half hour southwest of Rapid City, SD.
There you'll find the Alpine Inn - they have several lunch choices but only two dinner choices - one including meat and one vegetarian. Both are excellent. Great desserts! If you don't get there before opening time you'll be waiting in a long line (worth the wait).
Comfort Inn in Hill City is very nice. Only open until the last day of October I think.
The Mammoth museum in Hot Springs, SD is amazing if you are impressed by archeology and mammoth skeletons.