The circulating collections in Sawyer and Schow libraries are organized by the Library of Congress classification system. This system assigns a call number (a unique combination of letters and numbers) to each book. This call number is a unique identification and is what used to organized the books on the shelves.
The development of the Library of Congress classification system is a very interesting story. If you are curious and would like to know more, make an appointment with one of the Research Services librarians, we love talking about this!