Zodiac Killer letters to the San Francisco Chronicle

The unidentified Zodiac Killer mailed multiple taunting letters and cryptograms to Bay Area newspapers in 1969–1974, including the San Francisco Chronicle. The Chronicle received several of these communications, one of which contained a 408-symbol cipher that was solved by local schoolteachers shortly after publication. The letters played a central role in public awareness and the ongoing investigation into the Zodiac crimes.