The Charles Thom Papers cover materials from Thom's college years to biographical memoirs published after his death. The collection includes correspondence, notes, notebooks, essays, lectures, speeches, diaries, journals, and lantern slides from professional trips. There are also published items, including monographs, journal articles, and newspaper clippings. The majority of the collection focuses on soil microbiology, mycology, food spoilage, food poisoning, and penicillin.