Alexandra Day (born 1941) was largely self-taught as an artist, though she had an artist for a father, and spent a short time at the famous Art Students’ League in New York.
Alexandra and her husband started the Green Tiger Press in 1970 but it didn’t occur to her to try illustrating herself until a salewoman for the company suggested that a new version of “The Teddy Bears’ Picnic” would be popular. They didn’t have an illustrator who seemed right, so she illustrated it herself. That book is still in print, so I guess you could say it was a popular success!