Fort Mandan Overlook is so named because the site overlooks the area where Lewis and Clark established their headquarters, called Fort Mandan, in the winter of 1804-1805. Fort Mandan was a triangular fort which provided shelter, protection, and a place of cultural interchange between the explorers and the area's Indian inhabitants, for whom the fort was named. The original site of Fort Mandan was beside the river and has been inundated.