When we were done browsing the National Buffalo Museum, we spent some time walking around the Frontier Village in Jamestown. It's right outside the museum and you have to go through it if you want to get to the World's Largest Buffalo.
It is free (although there is a donation bin at the entrance if you feel so inclined) and there is a lot more set up than I realized from the Internet.
There are also some actual businesses here (like this one below; no pictures from inside) if you get here before 5 or 6pm, when most of them close.
The rest of the village doesn't really close until late in the evening, so we wandered around town and peeked into all the buildings. There are a lot of buildings and most of them are set up really nicely.
You can also take a pony or carriage ride.
Mannequins are my nemesis, but hopefully you don't suffer from the same infliction. There are several fake people scattered throughout the village.
I thought the school house was the most well done (even though there were lots of mannequins here).
They didn't make things for tall people in the 1800s (Eric is 6'2").
We saw more surveying equipment (and surveying exhibits) on this trip than animals.
Free, easily seen, and something to do to get out and stretch your legs in North Dakota! Try to get there before 5pm to check out the shops, but even after business hours it's neat to see all these set-ups in one place.