Emerging from decades of turmoil, late nineteenth-century Mexico City was a capital in transition. Yet as the city (and its republic) embraced technological and social change, it still faced perceptions of widespread crime and disorder. Accordingly, the Porfirian government relied on an elite group of government officials, prominent citizens, politicians, urban professionals, and newspaper editors to elevate the Mexican nation from its perceived backward condition. Influenced by prevailing social theories, such as positivism and social Darwinism, this ruling class sought not only modernization but also the imposition of national morals. While elites sought to guide and educate the middle class toward this ideal, they viewed the growing underclass with apprehension and fear. Through a careful examination of judicial records, newspapers, government documents, and travelers’ accounts, The Imagined Underworld uncovers the truth behind six of nineteenth-century Mexico’s most infamous crimes, including those of the serial killer “El Chalequero.” During his sensational trial, ruling elites linked the killer’s villainous acts with the impoverished urban world he inhabited and victimized. This pattern was not limited to the most nefarious criminals; rather it would be repeated for all crimes committed by the poor. In an effort to construct a social barrier between the classes, elites invented a dangerous urban periphery populated by imaginary Mexicans—degenerate, deviant, and murderous. However, the Porfirian elite did not count on middle-class and police involvement in crime—and in numerous incidents, including a deadly love triangle, elites were betrayed by their own role in criminality. By analyzing the cases used to forge the underworld and those that defied its myth, Garza uncovers the complex reality that existed beyond the Porfirian ideals of order and progress.