Double Ditch, on the Missouri River north of Bismarck, preserves a major Mandan earth lodge village occupied from about 1450 to 1785. Named for two visible fortification trenches, the site also contains midden mounds, defensive ditches, palisades, and traces of a settlement once larger than the surviving earthworks suggest. Archaeological survey identified additional outer ditches and showed that the village grew large near its founding, then steadily contracted over time. By the mid-18th century, only a much smaller community remained. Archaeologists link this decline to drought or disease, and the village was abandoned after the smallpox epidemic of 1775 to 1782.