MonDak Heritage Center
No admission feeAn art and history museum in Sidney, Montana, with exhibits on the local region plus art classes, events, and a research library.

Photo: Xerxes2004, CC BY-SA 3.0, via Wikimedia Commons. Cropped and resized.
Walk through a partly rebuilt fur trading post on the upper Missouri, with a museum inside the red-roofed Bourgeois House.
15550 Highway 1804 · Williston, ND
From 1829 to 1867 this was the most important fur trading post on the upper Missouri River, capitalized by John Jacob Astor's American Fur Company. Today you walk through a partial reconstruction rebuilt to reflect the fort in 1851, when the buffalo robe trade peaked. The visitor center and museum sit in the Bourgeois House, and the trade house, trade room and clerk's office open seasonally. No entrance pass is required.
The closest stops to Fort Union Trading Post National Historic Site, ordered by straight-line distance.