Here is an interesting article, The History of Children's Books written in January, 1888 by C.M. Hewins in the Atlantic Monthly. Yes, 1888.
In it, Hewins tracks the emergence of children's books in the English speaking world from the 1430's onwards, with some intriguing commentary of the development of this branch of literature in the USA.
Interesting to see these views and this synopsis in that year, just before children's literature really began to bloom in the US.