I got a thing for old mining towns, and Lead South Dakota would certainly qualify.
Dude...
The 1880 train in the Black Hills would 110% be your kinda thing. It's friggin awesome.
It's an hour long narrated train ride between Keystone and Hill City, both former mining boom towns. Goes through the mountains and there's lots of old mining homesteads and claims, etc. It goes through National Forest land, the scenery is unreal.
It's kinda cool thew way it works. It runs back and forth, basically you buy a ticket for each way and pick your time. What my kid and I do is get on in Hill City, and we pick our return trip for later in the day. That gives us time to bum around and hang out in Keystone which is a super cool little town with great places to eat and lots of local shops that aren't just the touristy, "buy a bag of rocks' type places. There are lots of local crafts people making some really cool shit.
You get some really great views of Black Elk Peak (formerly Harney Peak, highest point east of the Rockies and west of the French Pyrenees.) and there's a lot of wildlife as well. Side bar, there are some awesome hikes up BEP, I've done 5 different routes and if you ever go I can give you some guidance there.
If you like history and science, the Mammoth Site is in Hot Springs just a short drive away which is one of the coolest things you can do there. Jewel Cave is also a must-do, it's mining-related but there's a lot more to the story, I'll let you google it for funsies. Also, if you go there skip the main tour that they call the Scenic Tour. It's ok, but it's a bazillion people on each go round, and you're gonna put up with the typical idiots trying to touch everything, talk over the tour guide, and babies crying.
What you want is the Historic Lantern Tour. It's fucking great. Basically you're in a small group of about 6-8 people, and you get your own guide who's an actual employee of NPS. The guides are all actually cavers in real life who do exploration, and they're cool as hell to listen to. The coolest part is that the tour is designed to be a reproduction of the first tours offered by the guys who discovered the cave back in the 20s. The tour guides wear the original 1930s park ranger outfits, and they take you places you don't get to see in the vanilla tour. You go in a completely separate entrance and get the history of the two dudes who discovered it by accident, and everyone carries old-style oil lanterns like they had in the 30s. It's badass.
Sorry man, I nerd out on that kind of stuff. It's up my alley more than the typical vacation stuff people do.