A la Recherche des Femmes Perdues (“In Search of Lost Women”), is a digital humanities project about the book On Prostitution in the City of Paris (De la prostitution dans la ville de Paris), a monumental and precocious work of social science and a precursor for literary realism. It was published in French in 1836 by Alexandre Parent du Châtelet, an aristocratic doctor and social engineer who had previously designed the famous Paris sewers. On Prostitution in the City of Paris was vital in justifying and publicizing the first national system of prostitution regulation. It was also a triumph of both quantitative and qualitative research, one of the first studies to deploy statistical methods on any topic, and the first to draw upon prostitutes’ own experiences through hundreds of interviews. These experiences, and the popular opinions and prejudices he documented, were a source of information not only for subsequent scientists, but also for journalists, novelists, and other artists.