Nearby town: Williston, ND; Sidney, MT
Fort Union was the busiest and most important fur trade post in the Upper Missouri for most of the 19th century. It was located near the confluence of the Missouri River and the Yellowstone River on the present-day border of North Dakota and Montana.
Fort Union was built in 1828 and became the headquarters of American Fur Company. The Company was founded and managed by John Jacob Astor. Astor, an immigrant from Germany, made a fortune in the fur trade (predominantly beaver) and became the first multi-millionaire in the United States.
Many tribes (Assiniboine, Crow, Ojibwe, Lakota) were involved in the trade at the post, trading furs and pelts for guns, blankets, alcohol, etc. Beaver fur (used for hats that became very popular in Europe) was the main commodity in Fort Union's early days. However, once beaver hats dropped out of fashion in the 1840s or so, the trade primarily transitioned to buffalo (bison) hides.
The Fort has been partially reconstructed and is a great and interesting roadside stop, spend about an hour or two exploring the grounds and going through all the exhibits at the excellent museum.
The centerpiece of the fort is the impressive Bourgeois (manager's) house.
A number of famous people stayed at Ft. Union during their western expeditions: including Father De Smet, Hugh Glass, Jim Bridger, and John James Audubon.
For more info: https://www.nps.gov/fous/index.htm
