Pinkerton National Detective Agency

Allan Pinkerton founded a detective agency in Chicago that originally gained fame for solving a series of train robberies and later became known for helping management break strikes by the new labor unions.
Pinkerton became famous when he claimed to have foiled a plot to assassinate president-elect Abraham Lincoln, who later hired Pinkerton agents for his personal security during the Civil War. After the war, Pinkerton returned to running his Agency, which made its name in a number of high-profile cases, including that of Frank and Jessie James. By the 1870s, the agency had the world's largest collection of photographs of criminals and suspects.