Griswold was one of the early proponents of teaching schoolchildren American poetry in addition to English poetry. One of his anthologies, "Readings in American Poetry for the Use of Schools", was created specifically for that purpose. His knowledge in American poetry was emphasized by his claim that he had read every American poem published before 1850—an estimated 500 volumes. "He has more literary patriotism, if the phrase be allowable ... than any person we ever knew", wrote a contributor to "Graham's". "Since the Pilgrims landed, no man or woman has written anything on any subject which has escaped his untiring research." Oliver Wendell Holmes, Sr. noted that Griswold researched literature like "a kind of naturalist whose subjects are authors, whose memory is a perfect fauna of all flying and creeping things that feed on ink."