How are biographies ordered in the library?

Most books are commonly ordered by their Dewey number plus the first three letters of the author’s last name. Individual biographies on the other hand are ordered differently. General biographies–usually about a group of similar people–are categorized under 920 in the usual way by the author’s last name. However more specific biographies about individuals and their areas of interest are given the 921-928 call numbers.  At our library at ISB we limit all our individual biographies to 921. To mix it up, the person the biography is about is the name listed on the spine label–not the author’s last name. This makes finding biographies a little easier since all you have to do is look for the individual’s last name within the 921 collection.  The 929 section is dedicated to genealogy: that’s the study of names.