Koko, the beloved gorilla who was able to communicate in more than 1,000 signs, has died at 46 in California's Santa Cruz mountains.
Just three years later, Dr. Francine "Penny" Patterson and Dr. Ronald Cohn moved Koko, a second gorilla named Michael and the project to Stanford University and went on to establish The Gorilla Foundation.
"She was beloved and will be deeply missed".
It grew into a decades-long friendship that revealed a deeper side of Koko and her ability to understand, though some experts questioned Patterson's methods and Koko's abilities.
"Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy", the organization stated in a press release.
Koko appeared on the cover of her first National Geographic in 1978 and featured a picture she had taken of herself in the mirror.
The foundation says it will honor Koko's legacy with a sign language application featuring Koko for the benefit of gorillas and children, as well as other projects.
Her love of animals spawned the children's book "Koko's Kitten" and her own branded line of toys.
Koko once met Robin Williams in a now-famous encounter.
Throughout her life, Koko adopted several felines, using sign language to give them names like All Ball, Lipstick and Smoky.