Allan Pinkerton was born in 1819 in the Gorbals slum of Glasgow, left school at 10 after his policeman father died, and became a cooper and a member of the Scottish Chartist movement. In 1842 he and his wife Joan fled to North America, either to dodge arrest or, by a darker theory, to escape fellow Chartists who suspected him of informing. Shipwrecked on Sable Island, the couple settled in Dundee, Illinois, where Pinkerton stumbled onto a counterfeiters’ camp while hunting for barrel wood, staked it out, and handed the sheriff a clean set of arrests. Chicago made him its first police detective in 1849, and in 1850 he founded the agency whose open-eye logo and motto, We Never Sleep, gave the world the term private eye.

While guarding railroads for profit, Pinkerton ran an Underground Railroad stop, met Frederick Douglass, and gave John Brown $500 and help buying supplies for Harpers Ferry. His agents, led by Kate Warne, foiled the Baltimore plot against President-elect Lincoln, but as George McClellan’s intelligence chief he sometimes doubled or tripled Confederate troop counts. After the war came the failed hunt for Jesse James, an 1872 contract to help Spain suppress a Cuban revolution aimed at ending slavery, and his death in 1884. Under his sons, the agency became the strikebreaking force behind the Anti-Pinkerton Act of 1893.

• His agency recovered $688,000 of a $700,000 train safe robbery using surveillance, undercover work and daily written reports.
• Kate Warne became the first female detective in the United States and is buried beside Pinkerton and his wife in Graceland Cemetery.
• Posing as Confederate Major E. J. Allen, Pinkerton was recognized in Memphis and barely escaped.
• Historians split over the inflated estimates: T. Harry Williams called the service incompetent, while Edwin Fishel and James Mackay blame McClellan’s biases.
• Accounts of his death range from gangrene after biting his tongue in a fall to a stroke or malaria from his wartime undercover work.