Secret Six
Part of Chicagoland Chamber of Commerce (previously the Chicago Association of Commerce)
Architectural detail from the exterior of the St. Clair Hotel, which served as the Secret Six's makeshift jail
Operation name	Secret Six
Part of	Chicagoland Chamber of Commerce (previously the Chicago Association of Commerce)
Type	Vigilante
Scope	Chicago, Illinois but with efforts nationwide
Participants
Initiated by	Col. Robert Isham Randolph
Mission
Objective	Investigation and prosecution of murder, bombing, kidnapping, extortion, bank robbery and other crimes in Chicago and elsewhere, with a particular focus on racketeers, including Al Capone
Timeline
Date begin	February 8, 1930
Date end	January 17, 1933
Duration	3 years

The Secret Six, officially known as the Crime Prevention and Punishment Committee of the Chicago Association of Commerce (CAC), was a well-funded and powerful vigilante enterprise established by the Association (now the Chicagoland Chamber of Commerce) in February 1930. The group inspired a movie by the same name, was credited by Al Capone for his downfall, helped launch Eliot Ness and his Untouchables, and briefly served as a model for vigilante organizations across America. The Secret Six investigated dozens of bombings, kidnappings, extortion cases, bank robberies, and other crimes, solving some of them and winning nationwide fame. However, after a series of mistakes and scandals, including accusations of bigamy, recklessness, and other improprieties against its agents, and a widely-publicized false-arrest lawsuit, the organization folded in January 1933.