Cooper's papers fall into two almost equal categories: teaching materials and research materials. The teaching materials are largely files of examination questions, with Cooper's notes and drafts and occasionally some worked answers by students. These cover undergraduate courses at McGill and Sir George (1936-1969), special subjects, Ph.D. comprehensives, graduate and honours papers (1937-1967), historical method and philosophy of history (1937-1961), and McGill and Sir George courses in Latin American history (1937-1961). Course materials include an outline for an extension course in Canadian history (ca 1950), and notes for a course in 18th century diplomacy. A file of correspondence on History Department business (1952) largely concerns a doctoral thesis for which Cooper was external examiner. Other files contain lists of graduate student papers (1964-1966). Cooper's research files contain his notes, and occasionally some correspondence, on Latin American and West Indian history, early American historiography, banking and shipping in Québec and the history of higher education in the United States and Québec. His notes on historiography and 18th century diplomacy were probably gathered for the courses he taught in those subjects, and there are about 20 cm of index cards on mercenary regiments in the Crimea. There is a file of correspondence with the British Museum concerning Colonial maps, and one of correspondence and memoranda on Cooper's proposal for a history of McGill (1949). As well, there is a file of correspondence relating to the Klieforth Prize and the publication of Cooper's winning manuscript (1947-1949). Finally, a copy of Cooper's draft article for the Dictionary of Canadian Biography on James and Andrew McGill reflects his interest in Montréal and McGill history.