This project tells the story of how for six decades beginning in the 1870s private detectives conducted investigations that reached into American workplaces, leisure activities, and homes. They operated as a de facto national police force, filling a gap in policing services at the state and federal level that existed until the expansion of the FBI in the 1930s. Railroad corporations hired them for investigations of train robbery, and later banks and jewelers retained them to investigate robbery, theft, and burglary, and local police and prosecutors turned to them in cases of murder, bombing, and kidnapping. Business owners employed those same detectives to conduct surveillance in workplaces and to infiltrate radical political groups and labour unions, a practice that ended only after attention from a Congressional committee in the late 1930s. Private organizations tasked investigators with locating the illegal liquor sales, gambling, and prostitution, while individuals set them to watch suspected adulterers.
This project will be the first study to bring together all the activities of private detectives so that they can shed light on each other. When taken together, they reveal personal surveillance of a far larger scale and broader scope than has been recognized. I also extend those analyses by focusing on the practices of private investigation not just its subjects.