Penn's online catalog Franklin contains records of books, journals, newspapers and other items owned by all the libraries of the University of Pennsylvania except the law library. When you find records for books or journals, you will most often be given a call number with which you can locate it. The Penn Libraries mainly use the Library of Congress call number system, which is explained here. To learn more about the subjects associated with call numbers, look at the Library of Congress classification outline.

Some books and journals at Penn are still classified with the Dewey Decimal System.