This article reconstructs the life of Marie Piquemal, a French woman turned colonial madam, to explore the world of white prostitution in colonial Dakar, Senegal, in the first half of the twentieth century. White brothel prostitution required the migration of white French women from the metropole to supply these institutions. By providing white French men with sexual access to white sex workers, brothel keepers like Piquemal helped to curb the development of interracial intimacy at a time when sexual-conjugal unions across the color line were becoming increasingly controversial. This article thus argues that brothel keepers played a key role in reifying racial boundaries upon which colonial rule rested, especially within an empire that claimed to be race blind. Although French authorities were aware of the migration of French women for sexual labor between metropole and colony, they condoned this process in an effort to maintain the racial status quo.