I grew up partly in Bismarck and this used to be one of my favorite places to go. I think I must have gone at least once a month. It provides a rich history of Bismarck (and ND) and they've since updated the museum portion to include dinosaur findings (which is really cool). Great for kids. Great for the family. I see more details every time I go. They also have a unique gift shop.
Pros: Rich history, great artifacts, good for family