(1819-84) an American, born in Scotland, who established the first US company of private detectives (= people who investigate crimes but are not members of the police). He began the Pinkerton National Detective Agency in 1850 in Chicago. Its advertisements showed a large eye, with the words 'We never sleep'. Pinkerton also established a US organization during the Civil War which later became the US Secret Service. The company today operates in 20 countries and provides protection for large companies.