Pettee was particularly proud of her handling of Christian Literature and considered it a unique feature of her
system. Additionally, she held a particular view of the way biographies should be handled. Pettee stated, “I have
a firm conviction as to what to do with biography. It seems to me that the biography of a man is most usefully
classed with the subject to which he contributed his major life’s work.”19 Each of the sections Pettee developed was
carefully nuanced using her experiences, her personal handling of theological materials, and her own method of
delicate logic. Using her rules, Pettee reclassified over 165,000 books at the Union Theological Seminary Library.20
Her classification system would hence be known as Union Classification.