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Library of Congress Call Numbers

The Library of Congress (LC) classification system groups together books on similar subjects by their call numbers.


There are 21 main LC call number classifications or classes. Within these, there are also sub-classifications, which are listed on the linked PDFs.

Reading the number

ex: HN59 .T39 2014
HN First letters: The first letter of a Library of Congress call number indicates the general class the call number falls within. In our example, the book is located under H, which is where books on social sciences are classed. If there is a second or third letter, these indicate a specific subclass. HN indicates social history and conditions, social problems and social reform.

Numbers that follow the letters: The numbers define the subject of the book. The number 59 is referring to a book about a specific region or country in this case, America.


Cutter Number (the next set of numbers)The Cutter Number indicates the author or title of the book. It is taken from a table matching names or titles to a set of numbers. In our example, .T39 reflects the first word of the author, Taylor.

2014 Year number: The edition of a volume is the next part of the call number. The year of publication follows the Cutter number to indicate the edition. In our example, 2014 indicates that this edition was published in 2014.