Fort Union  -  Fort Union Trading Post National Historic Site, ND.  Both Lewis and Clark thought the confluence of the Missouri and Yellowstone rivers would be an excellent strategic location for a future fort and trading post.  The original Fort Union was built at this location in 1828 for John Jacob Astor's American Fur Company.  It became a major center and was very successful in building trade with the Plains Indians.
Photo:  ©Charley Van Pelt