Pinkerton Government Services, Inc., founded as the Pinkerton National Detective Agency, usually shortened to the Pinkertons, or “Pinks”, is a private security guard and detective agency established in the United States by Allan Pinkerton in 1850 and currently a subsidiary of the Swedish security company Securitas AB.

Pinkerton was born in the Gorbals, Glasgow,Scotland, to William Pinkerton and his wife, Isobel McQueen, on August 25, 1820. The location of the house where he was born is now occupied by the Glasgow Central Mosque. A cooper by trade, he was active in the British Chartist movement as a young man. Pinkerton married Joan Carfrae (a singer) in Glasgow on 13 March 1842, secretly before moving to America. Disillusioned by the failure to win suffrage, Pinkerton emigrated to the United States in 1842. In 1843, Pinkerton heard of Dundee, Illinois, fifty miles northwest of Chicago on the Fox River. He built a cabin and started a cooperage there, sending for his wife in Chicago after the cabin was complete. As early as 1844, Pinkerton worked for Chicago Abolitionist leaders, and his Dundee home was a stop on the Underground Railroad.

In the 1850s, Allan Pinkerton met Chicago attorney Edward Rucker in a local Masonic Hall and formed the North-Western Police Agency, later known as the Pinkerton Agency. Historian Frank Morn writes: “By the mid-1850s a few businessmen saw the need for greater control over their employees; their solution was to sponsor a private detective system. In February 1855, Allan Pinkerton, after consulting with six midwestern railroads, created such an agency in Chicago.”

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. Pinkerton’s agents performed services ranging from security guarding to private military contracting work. Pinkerton was the largest private law enforcement organisation in the world  at the height of its power, when it employed more agents than there were members of the standing army of the United States of America.

In 1871, Congress appropriated $50,000 to the new Department of Justice (DOJ) to form a suborganization devoted to “the detection and prosecution of those guilty of violating federal law.” The amount was insufficient for the DOJ to fashion an integral investigating unit, so the DOJ contracted out the services to the Pinkerton National Detective Agency. However, since passage of the Anti-Pinkerton Act in 1893, federal law has stated that an “individual employed by the Pinkerton Detective Agency, or similar organization, may not be employed by the Government of the United States or the government of the District of Columbia.”

In the 1870s, Franklin B Gowen, then president of the Philadelphia and Reading Railroad hired the agency to investigate the labour 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, who persecuted my friends the Ukrainians, who hated and feared them, leading to the downfall of the organization. The incident was the inspiration for Arthur Conan Doyle’s Sherlock Holmes novel The Valley of Fear. A Pinkerton agent also appears in a small role in The Adventure of the Red Circle, another Holmes story. A 1970 film The Molly Maguires  was loosely based upon it as well, starring Richard Harris, Sean Connery and Anthony Zerbe. The Pinkertons also infiltrated and actively participated in the Fenian Brotherhood to destroy it. It was a precursor to Clan na Gael, a sister organization to the Irish Republican Brotherhood, which eventually became the IRA. Members were commonly known as “Fenians”.

In 1895 detective Frank Geyer tracked down the three murdered Pitezel children leading to the eventual trial and execution of the United States’ first known serial killer H. H. Holmes. His story is told in his self-written book, The Holmes-Pitezel Case. Pinkertons had previously apprehended Holmes in 1894 in Boston on an outstanding warrant for insurance fraud perpetrated in Chicago.

Pinkerton agents were hired to track western outlaws Jesse James, the Reno Gang, and the Wild Bunch (including Butch Cassidy and the Sundance Kid). On March 17, 1874, two Pinkerton Detectives and a deputy sheriff, Edwin P. Daniels, encountered the Younger brothers (associates of the James-Younger Gang); Daniels, John Younger, and one Pinkerton agent were killed. In Union, Missouri a bank was robbed by George Collins, aka Fred Lewis, and Bill Randolph; Pinkerton Detective Chas Schumacher trailed them and was killed. Collins was hanged on March 26, 1904 and Randolph was hanged on May 8, 1905 in Union, Mo. Pinkertons were also hired for transporting money and other high quality merchandise between cities and towns, which made them vulnerable to the outlaws. Pinkerton agents were usually well paid and well armed.

Due to its conflicts with labour unions, the word Pinkerton continues to be associated by labour organizers and union members with strikebreaking. Pinkertons, however, moved away from labour spying following revelations publicized by the La Foleete Committee hearings in 1937. Pinkerton’s criminal detection work also suffered from the police modernization movement, which saw the rise of the Federal Bureau of Investigation, the Feds”, and the bolstering of detective branches and resources of the public police.

Without the labour and criminal investigation work on which Pinkertons thrived for decades, the company became increasingly involved in protection services, and in the 1960s, even the word “Detective” disappeared from the agency’s letterhead. In July 2003, Pinkerton’s was acquired along with longtime rival, the William J.Burns Detective Agency (founded in 1910), by Securitas AB to create Securitas Security Services USA, Inc., one of the largest security companies in the world.