The Zodiac Killer is an unidentified serial killer who operated in Northern California during the late 1960s and early 1970s. The killer is known for committing at least five murders between 1968 and 1969 and for sending taunting letters to local newspapers, some of which included cryptograms. The case remains one of the most famous unsolved criminal mysteries in American history. Despite extensive investigations by law enforcement and amateur sleuths, the true identity of the Zodiac Killer has never been confirmed. The killer's letters and the cryptograms have intrigued many, leading to numerous theories and suspects, including Arthur Leigh Allen and Gary Francis Poste. The Zodiac Killer's story continues to captivate the public and inspire books, films, and documentaries.