The killing spree began on 20 December, 1968 when a couple was shot dead while sitting in a car on Lovers Lane in San Francisco, and it lasted for 10 months.
The Zodiac is known to have killed at least five people, but the fact he got away with these crimes is only partly why they're so notorious. This shadowy serial killer toyed with police and reporters at the time, goading them with cryptic, coded messages.
Doubt over the authenticity of the notes was banished when their author mailed in a piece of bloodied clothing that had belonged to one of his victims.
Several suspects have been considered over the years, but the Zodiac's identity remains unknown and the case is still officially open in Napa County and Riverside.
David Fincher's 2007 film Zodiac, starring Jake Gyllenhaal and Robert Downey Jr, explores the case and the impact it had on those who were directly involved with it.