Major P. H. G. Powell-Cotton, an early East African explorer, was the first European to contact a small mountain group calling themselves the So (singular: Sorat) in 1902 on the upper slopes of Mount Kadam and Mount Moroto during his exploratory trip through what is now Karamoja District, Uganda (1904, pp. 305 ff.). From that time until we carried out field-work among them in 1969-70 very little has been written about the So. Today they inhabit three of the four tertiary volcanic mountains in Karamoja: Mounts Kadam, Moroto, and Napak. The approximate distances between these mountains in statute miles are: Moroto-Kadam, 40; Moroto-Napak, 38; and Napak-Kadam, 32. The So are surrounded on all sides by semi-nomadic pastoral groups including the Karamojong, Turkana, and Suk. In our census of the Lia and Naukoi valleys on the western slopes of Moroto Mountain—the area primarily covered by our study—we found approximately 1,700 So. The total population probably does not exceed 4,800 on all three mountains.