Fort Union Trading Post National Historic Site
John Jacob Astor's American Fur Company built Fort Union Trading Post in 1828 near the junction of the Missouri and Yellowstone rivers in what is now North Dakota. In it's heyday, the post was a busy place and employed up to 100 people. It became the headquarters for trading buffalo hides and other furs with the Assiniboine, Crow, Cree, Ojibway, Blackfeet, and Hidatsa Tribes.
Plane - Commercial flights are available through Williston ND and Sidney MT.