This chapter traces the expansion of Baltimore’s sex trade during the Civil War and the reactions of civilian and military authorities to its growth. Baltimore was an occupied city and staging ground for Union troops for much of the war, and the presence of thousands of soldiers in and around the city swelled the demand for commercial sex. As the economic hardships that accompanied war drove more women into sex work, Baltimore’s prostitution trade expanded far beyond its antebellum scale. Prostitution drew the attention of military and civil authorities, who were fearful of the potential the brothels had to undermine military discipline, civilian relations, and the health of soldiers. Baltimore’s brothel keepers managed to keep Union officials at bay by cooperating with their efforts to round up errant troops and providing valuable intelligence gathered from their clients, and many managed to make small fortunes by catering to soldiers. However, the attention the war brought to the violence, disorderliness, and disease-spreading potential of the sex trade would have profound long-term consequences for Baltimore’s sex workers and their enterprises.