Pinkerton (detective agency) significant person James McParland
Molly Maguires
In the 1870s, Franklin B. Gowen, then president of the Philadelphia and Reading Railroad, hired the agency to "investigate" the labor unions in the company's mines.  A Pinkerton agent, James McParland, using the alias "James McKenna", infiltrated the Molly Maguires, a 19th-century secret society of mainly Irish-American coal miners, leading to the downfall of the labor organization.
The incident inspired Arthur Conan Doyle's Sherlock Holmes novel The Valley of Fear (1914–1915). A Pinkerton agent also appears in a small role in "The Adventure of the Red Circle", a 1911 Holmes story. A 1970 film, The Molly Maguires, was loosely based upon the incident.