A Beaux-Arts architect left nothing to chance, assiduously designing every aspect of a commission. Even the lamppost, such as the one above, received first class treatment, and was not purchased on-line from Home Depot.
The flag pole, above and below, also has a wealth of ornamentation and symbolism.
Griffins and other allegorical figures that probably represent commerce or agriculture (that is perhaps Ceres on the boat to the right) signify the bounty produced by the knowledge held in libraries. Also, griffins protected treasures, such as the wealth of knowledge held in books.