In 1600 they were the largest, most technologically advanced indigenous group in northwest Mexico, but today, though their descendants presumably live on in Sonora, almost no one claims descent from the Ópatas. The Ópatas seem to have “disappeared” as an ethnic group, their languages forgotten except for the names of the towns, plants, and geography of the Opatería, where they lived. Why did the Ópatas disappear from the historical record while their neighbors survived? David Yetman, a leading ethnobotanist who has traveled extensively in Sonora, consulted more than two hundred archival sources to answer this question. The result is an accessible ethnohistory of the Ópatas, one that embraces historical complexity with an eye toward Opatan strategies of resistance and assimilation. Yetman’s account takes us through the Opatans’ initial encounters with the conquistadors, their resettlement in Jesuit missions, clashes with Apaches, their recruitment as miners, and several failed rebellions, and ultimately arrives at an explanation for their “disappearance.” Yetman’s account is bolstered by conversations with present-day residents of the Opatería and includes a valuable appendix on the languages of the Opatería by linguistic anthropologist David Shaul. One of the few studies devoted exclusively to this indigenous group, The Ópatas: In Search of a Sonoran People marks a significant contribution to the literature on the history of the greater Southwest.