Why is detective fiction so popular? What connects such diverse characters as the 'armchair sleuth', the 'hardboiled dick', and the police detective? Dime Novels and the Roots of American Detective Fiction uncovers the significance of often-neglected dime novels in revealing early examples of the subgenres of detective fiction - drawing-room mysteries, hardboiled 'tough guy' fiction, police procedurals, and postmodern detective fiction - in the genre's first mass instantiation in the dime novels (1860-1915). A study of over 100 dime novel endings shows the prevalence of subversive representations of gender, race and class, while new readings of iconic detectives like Nick Carter and Allan Pinkerton reveal the enormous influence of these figures on future developments in the detective genre. The book argues that inherent tensions between subversive and conservative impulses - theorized as contamination and containment - explain detective fiction's ongoing popular appeal to readers and to writers such as Twain and Faulkner, whose detective writings are clearly informed by dime novels.