The Invention of Female Biography brings together essays that describe, elucidate and conceptualize the exhaustive research, unique editorial challenges and innovative responses of participants in the Female Biography Project. Scholars representing multiple disciplines, languages, historical eras and critical perspectives report on the idiosyncratic difficulties and discoveries they encountered in annotating entries of varying lengths. This chapter considers the challenges Mary Hays faced as a female autodidact in the early nineteenth century. The Invention of Female Biography explores newly minted knowledge about individual women, both the knowledge that Hays accumulated as well as new research on the subjects, and considers how this modifies the understanding of specific figures and groups of women and their importance in their time. It demonstrates the unforeseen obstacles to retracing Hays's research and makes the case that by naming and illustrating 'female biography', Hays retooled existing practices for compiling catalogues of women.