The large and powerful Arikara, Mandan, and Hidatsa villages had long prevented the Lakota from crossing Missouri. However, the great smallpox epidemic of 1772–1780 destroyed three-quarters of these tribes. The Lakota crossed the river into the drier, short-grass prairies of the High Plains. These newcomers were the Saône, well-mounted and increasingly confident, who spread out quickly. In 1765, a Saône exploring and raiding party led by Chief Standing Bear discovered the Black Hills (the "Paha Sapa"), then the territory of the Cheyenne. Ten years later, the Oglála and Brulé also crossed the river. The Cheyenne then moved west to the Powder River country, and the Lakota made the Black Hills their home.