Clonalis House holds an important archive of books, pamphlets and manuscripts relating to the affairs of the family of O'Conor Don, Co. Roscommon, from the late 16th century onwards. Included among this material are papers and letters of the great eighteenth-century man of letters Charles O'Conor of Bellanagare (1710–1791). Many of his Irish manuscripts were transferred to Stowe by his grandson, Fr Charles, from where they eventually reached the Royal Irish Academy in the 1880s. A small few such as the Book of Magauran (on ISOS: National Library of Ireland), and the Book of the O'Conor Don were kept at Clonalis. Other Irish language material associated with Charles O'Conor, such as his memorandum books, also survived at Clonalis.
Gareth W. Dunleavy and Janet E. Dunleavy, The O'Conor Papers: a descriptive catalog and surname register of the materials at Clonalis House (Madison; University of Wisconsin Press 1977)
Catherine Coogan Ward and Robert E. Ward, The letters of Charles O'Conor of Belanagare (Ann Arbour, Michigan 1980)