Andreassen's papers fall into three series: personal materials, diaries, and professional files. Personal materials include family correspondence, 1929-ca 1932, and ca 30 cm of class notes and draft papers stemming from his student years, largely at Louisiana State. There are also files of private correspondence, some addressed to Mrs Andreassen, from the period 1975-1980. Andreassen's diaries cover the years 1936-1940, 1945-1952, 1962-1965, and 1968-1976. They record the working day and are interleaved with memoranda and correspondence, often of a personal nature. Professional files vary in nature with each stage of Andreassen's career, but correspondence and reports are consistent elements. To these may be added copies of surveys and inventories of the Louisiana Historical Records Survey, expense accounts and photographs arising from his work for UNRRA, records of archival deposits and drafts on an institutional history prepared as Archivist of CNR, and annual reports written as McGill Archivist.