British artist Cliff Wright produced the ink and water colour illustrations, which were used for the covers of the 1998 classic Harry Potter and The Chamber of Secrets and the follow up the Prisoner of Azkaban, released the following year.
The Chamber of Secrets' illustration measures 22.5 inches by 19 inches and has a starting guide price of 20,000 US dollars (£12,126). It shows Harry and Ron Weasley in the flying Ford Anglia, with the wizard's owl Hedwig in the back seat.
The second sketch shows Harry and Hermione on Buckbeak the mythical Hippogriff, with bids starting at 12,500 US dollars (£7580) for the 5.5 inches by five inches artwork.
The pieces will be auctioned by Nate D. Sanders in Los Angeles on Thursday.
JK Rowling wrote seven novels in the wizarding series that were reproduced around the world and led to a hugely successful series of films.