Serial KillerUnsolved
The Zodiac Killer Ciphers
San Francisco, California, United StatesJuly 31, 1969
The Zodiac Killer sent four cryptographic ciphers to Bay Area newspapers in 1969 and 1970. Only two have been solved. The 340-character cipher was finally cracked in 2020 by an amateur team. The 13-character cipher remains unsolved. No suspect has ever been definitively identified despite intense amateur and professional investigation spanning over 50 years.