Since the 1960’s and 1970’s, ethnographic research on Jewish menstrual rituals known as niddah, Taharat HaMishpacha, or Family Purity has associated their practices with religious behavior. Much of this research organizes around questions of women’s agency within ostensibly patriarchally constructed religious practices that carry the potential to oppress its women practitioners. This premise is built upon a number of implicit assumptions about the history of today’s niddah practices: that niddah is observed exclusively by Orthodox Jews; that increasing rates of niddah observance correlate exclusively with the trend toward stricter observance levels among the Orthodox since the 1960s; and that this increasingly strict observance itself reflects a reactionary trend among the Orthodox community (a.k.a. tradition versus modernity). All these assumptions currently circulate, in various degrees, among the American Jewish lay community and are shared by a significant number of congregational rabbis. Until the 1990s, no history of niddah existed to either support or refute these assumptions. I initially intended that this project would provide future ethnographers with a comprehensive history of niddah in America during the past one and a half centuries. I engaged Victor Turner’s theory of Social Drama as a framework for understanding this history as a socio-cultural process, rather than as a series of less than related events. However, this study h*as resulted in the identification of many more specific assumptions about the decline and revival of niddah observance in the twentieth century, which are not supported by the scant evidence available. These challenged assumptions beg new directions for research; a thorough reworking of the history of niddah in America; and a fresh look at the literature advocating niddah produced in the 1990’s and early 2000’s. This genealogy as Social Drama presents niddah in twentieth century America as undergoing periods of crisis, negotiation, and reintegration. This drama was triggered by late nineteenth century concepts of religion, body, and ritual that undermined and ruptured the integrity of niddah as a bodily religious ritual practice. Niddah’s twentieth century social drama culminated in fresh articulations of a unique Jewish sexuality and Jewish marital ethic.