The Pinkerton National Detective Agency was a security guard agency established in the United States in 1850 by Allan Pinkerton. Businessmen hired Pinkerton guards to keep strikers and suspected unionists out of their factories, the most notorious example being the Homestead strike. The agency's logo, an eye embellished with the words "We Never Sleep" inspired the term "private eye." The "Pinkertons" were also used as guards in coal, iron and lumber disputes in Illinois, Michigan, New York and Pennsylvania, as well as the railroad strikes of 1877.

A Pinkerton agent, James McParlan, infiltrated the Molly Maguires, leading to the downfall of this secret organization, ending years of violence, intimidation, and murder.

Pinkerton became a brand name for security guard services provided by Securitas AB, which in 2004 opted to retire the brand name permanently.

Correction: Pinkerton Security is no longer however Pinkerton Investigations lives on!!