CliffsNotes was started by a Nebraska native named Cliff Hillegass in 1958. He was working at Nebraska Book Co. when he met Jack Cole, the co-owner of a Toronto book business, Coles, and publisher of a series of Canadian study guides called Coles Notes. Cole suggested that Hillegass create an American version. Hillegass started with booklets covering sixteen William Shakespeare titles. CliffsNotes now exist on hundreds of works. The term CliffsNotes has now come into modern usage, as a noun for notes of a similar nature to the original Cliffs Notes books.
John Wiley & Sons, a publisher of scientific and technical publications, bought CliffsNotes in 2001 from IDG Books.