This dissertation uncovers women healers' vital role in the eighteenth- and early nineteenth-century healthcare marketplace. Euro-American women healers participated in networks of health information sharing that reached across lines of class and gender, and included female practitioners in American Indian and African American communities. Although their contributions to the healthcare labor force are relatively invisible in the historical record, women healers in the Delaware Valley provided the bulk of healthcare for their families and communities. Nonetheless, apart from a few notable monographs, women healers' practices and authority remain understudied. My project complicates a medical historiography that marginalizes female practitioners and narrates their declining healthcare authority after the mid-eighteenth century due to the emergence of a consumer society, a culture of domesticity, the professionalization of medicine, and the rise of enlightened science, which generated discourses of women's innate irrationality. Using the Philadelphia area as a case study, I argue that women healers were not merely static traditional practitioners destined to fall victim to the march of science, medicine, and capitalism as this older narrative suggests. Instead, I assert that women healers of various classes and ethnicities adapted their practices as they found new sources of healthcare authority through female education in the sciences, manuscript authorship, access to medical print media, the culture of sensibility, and the alternative gender norms of religious groups like the Quakers. Building on a longstanding foundation of recognized female practitioners, medically skilled women continued to fashion healing authority by participating in mutually affirming webs of medical information exchanges that reflected new ideas about science, health, and the body. In addition, women doctresses, herbalists, apothecaries, and druggists empowered themselves by participating in an increasingly commercialized and consumer-oriented healthcare marketplace. Within this unregulated environment, women healers in the colonies and early republic challenged physicians' claims to a monopoly on medical knowledge and practice. The practitioners analyzed in this study represent a bridge between the recognized and skilled women healers of the seventeenth century and the female healthcare professionals of the nineteenth century. / History