The Pinkerton Detective Agency was founded by Allan Pinkerton and Edward Rucker, under the name of the North-Western Police Agency, in the 1850s.
Gorbals-born Pinkerton married Joan Carfrae - a singer - in Glasgow in March 1842 in secret, before emigrating to New York later that year.
The following year, he moved to Dundee, 50 miles northwest of Chicago and established a cooperage and a residential cabin, sending for his wife once it was complete.
By 1844, Pinkerton was working for the Chicago Abolitionist leaders, with his home a stop on the Underground Railroad.
He was appointed the first detective in the city of Chicago in 1849, and joined up with attorney Rucker the following year to form what would later become known as Pinkerton&Co., and eventually the Pinkerton National Detective Agency.
Pinkerton’s business logo was a wide open eye with the slogan ‘We never sleep’.
As the United States expanded, rail transportation increased.
The Pinkerton firm solved a number of train robberies in the 1850s, bringing the Scot into contact with Chief Engineer and Vice President of the Illinois Central Railroad George McClellan, and company lawyer Abraham Lincoln.
In the late 1850s, Pinkerton himself reportedly pioneered a number of investigative methods still in use today, such as shadowing - surveillance of a suspect, and ‘assuming a role’, or going undercover.
Following the outbreak of the Civil War, Pinkerton served as head of the Union Intelligence Service between 1861 and 1862. While accompanying Abraham Lincoln to his inauguration, Pinkerton foiled an alleged assassination attempt on the president’s life in Baltimore, Maryland.
Pinkerton’s agents often worked undercover as Confederate soldiers and sympathisers in a bid to obtain military intelligence, with the Scot himself assuming the soubriquet of Mayor EJ Allen.
He was succeeded as head of the Intelligence Service - the forerunner of the US Secret Service - by Lafayette Baker.
After his service with the Union Army, Pinkerton returned to tracking train robbers, including Jesse James. However, Pinkerton failed to capture the outlaw, and the railroad express firms withdrew their support, with Pinkerton continuing at his own expense.
Pinkerton gave up the chase after one of his own undercover agents was allegedly captured and killed by James.
Allan Pinkerton died in Chicago in July 1884. The cause of death is the subject of some debate, with certain sources claiming he had slipped on a pavement and bitten his tongue, resulting in deadly gangrene while others reported he had died of a stroke, or from malaria contracted during a visit to the southern USA.
At the time of his death, he was heavily involved in the development of a system that would centralise all criminal identification records - a database now maintained by the FBI.
He is buried in Graceland Cemetery in Chicago, and is a member of the Military Intelligence Hall of Fame.
Pinkerton Detective Agency still exists as Pinkerton, a subsidiary of the Swedish security firm Securitas AB.