Trappers and Hunters.
Fort Henry, North Dakota, located where the Yellowstone River meets the Missouri River, was established on October 1, 1822. It was constructed by a party of men led by Major Andrew Henry, who mounted the expedition for the purpose of establishing a fur trading outpost for the firm of Ashley and Henry. The supply depot for trapping expeditions and trading posts was in an area that now encompasses most of Montana, western North Dakota, parts of Wyoming, and into Canada.
However, Fort Henry was deemed too far from the mountains and abandoned in 1823.
The site of the fort was approximately 20 miles southwest of Williston, North Dakota, near the Montana – North Dakota state line.
Also See:
Forts & Presidios Across America
Trading Posts and Their Stories
Trappers, Traders & Path Finders
Sources:
Fort Wiki
Historic Marker Database
Kids Encyclopedia
Wikipedia