I guess I wold cast my vote for Fort Robinson. Maybe just because it is closer to me. I think it is a more open place less comerialism. There are other places of interest farly nearby, although maybe not so dramatic as Deadwood.
There is Toadstool Park, just a pile of rocks
The agate fossil site
The Old Bordeaux Trading Post (a large gun collection there)
Chadron State Park
Marie Sandoz Museum
Medora would be a good location, maybe a little farther than I would go, but the North Dakota Badlands are real interesting. Lots of history there, especially if you are interested in Theodore Roosevelt. I think Roosevelt was sort of a phoney, just a rich man who wanted the adventure of owning a ranch, Maybe a phoney on Sa Juan Hill also. He spent $80,000 for a ranch owned it about 8 years and lost $16,000 on the deal. Would be kind of an expensive adventure for most of us.
Just want to keep the idea alive.
Clarence