Aboriginal settlements of the Mandan are found along the Missouri River in North and South Dakota. Early historic documents suggest that before the smallpox epidemic of 1781 there were from six to nine Mandan villages along the Heart and Missouri rivers. Following the epidemic, these villages merged and moved north to the Knife River where Lewis and Clark found the Mandan living in the villages of Mitutanka and Nuptadi and the Hidatsa living nearby in three villages. David Thompson found the Mandan and Hidatsa sharing Villages, but by the time of Lewis and Clark, each village was inhabited primarily by members of a single tribe. The Mandan villages were composed of earthlodges arranged randomly around a central plaza with a shrine and ceremonial earthlodge. The earthlodges were constructed with four center support posts and an outer wall of smaller logs. Roof beams were laid close together from the wall to the center supports and covered with mats. Everything was covered with sod, so the whole structure took the shape of a windowless earthen dome with an elongated earth-covered entryway. Today, the Mandan and the associated Hidatsa and Arikara live in Modern ranch-style houses on the reservation.