What was the first animated Disney feature film that was not based on an existing story?

"The Lion King" is the first Disney animated feature not based on an existing story. In another sense, it is based on half the stories in classical mythology. It tells the tale of the birth, childhood and eventual manhood of Simba, a lion cub. The cub's birth is announced in the opening sequence of the movie, called "The Circle of Life," which is an evocative collaboration of music and animation to show all of the animals of the African veld gathering to hail their future king. The cute little cub is held aloft from a dramatic spur of rock, and all his future minions below hail him, in a staging that looks like the jungle equivalent of a political rally.

Of course this coming together of zebra and gazelle, monkey and wildebeest, fudges on the uncomfortable fact that many of these animals survive by eating one another. And all through "The Lion King" the filmmakers perform a balancing act between the fantasy of their story and the reality of the jungle. Early scenes show Simba as a cute, trusting little tike who believes everyone loves him. He is wrong. He has an enemy - his uncle Scar, the king's jealous brother, who wants to be king himself one day.