The Pinkerton National Detective Agency was founded in 1850 in Chicago by Allan Pinkerton. It was one of the first private detective agencies in the United States, and its agents played an important role in law enforcement in the nineteenth and early twentieth century. Pinkerton agents were employed to capture bank robbers, counterfeiters, and forgers, but they also were used to infiltrate labor unions and disrupt strikes.
Allan Pinkerton established offices throughout the country. A Pinkerton innovation was photographing criminals after arrest. The "mug shot" soon was adopted by police departments. By the 1870s the Pinkerton agency had the largest collection of mug shots in the world. Agents would clip out newspaper stories about a criminal and include this information in the criminal's file. When a crime was committed in town, the sheriff could send descriptions by witnesses to the agency, and the agents would provide a photograph and a detailed description of the suspect to law enforcement agencies in nearby communities.
In the late 1870s, coal mining operators in Pennsylvania hired Pinkerton agents to disrupt union organizing. Some agents infiltrated the Molly Maguires, a secret organization of Pennsylvania and West Virginia coal miners. After a long and highly publicized trial in which Pinkerton agents were witnesses, nineteen miners were hanged for crimes committed during the strike.
Pinkerton agents chased bandits across the United States after the Civil War, including the gang led by Jesse and Frank James. Robert Pinkerton, the son of Allan, led the group that followed and captured the Younger Brothers Gang in 1874. Pinkerton agents also pursued, unsuccessfully, Butch Cassidy (Robert Parker) and the Sundance Kid (Harry Longabough) as the pair robbed trains and banks in the southwestern United States in the late 1890s.
The Pinkerton agency remains in existence and has its headquarters in Encino, California. The agency provides investigative services, uniformed security officers, security systems, and other products and services associated with personal and business security.
Horan, James D. 1968. The Pinkertons: The Detective Dynasty That Made History. New York: Crown Publishers.
Morn, Allen. 1982. "The Eye that Never Sleeps": A History of the Pinkerton National Detective Agency. Bloomington: Indiana Univ. Press