To the southeast of Bainville is Fort Union Trading Post, a National Historic Site. The original fort built in 1828 by the American Fur Company, rose at the convergence of the Missouri and Yellowstone Rivers. By 1867, it was gone, as the fur trade was coming to a halt. Today's reconstructed version is managed by the National Park Service. It's well worth seeing anytime, but especially if you can make it on the occasion of the Fort Union Rendezvous, an annual event.