The Dewey Decimal System was created by Melvil Dewey in the 1800s. He was a library guy and was hired by a library in Massachusetts to run their library. However, he ran into a problem. While fiction books were easy to organize based on the author's last name, non-fiction books, books that are based on real facts, events or people, couldn't work the same way. Think about trying to look for a book about trees by author! It would be impossible, especially since many non-fiction authors and publishers write about multiple topics.