What was the first Disney film not to be based on an original story?

The first Disney film not to be based on an original story was "Snow White and the Seven Dwarfs," released in 1937. However, if you are asking about the first Disney animated feature that was not based on a fairy tale or original fable, that would be "The Jungle Book," released in 1967, which is based on Rudyard Kipling's works.