- 1920 to 1924 1
- 1925 to 1929 1
- 1930 to 1934 0
- 1935 to 1939 0
- 1940 to 1944 1
- 1945 to 1949 1
- 1950 to 1954 5
- 1955 to 1959 6
- 1960 to 1964 16
- 1965 to 1969 18
- 1970 to 1974 1
- 1975 to 1979 1
The preservation of the Duke University Libraries Digital Collections and the Duke Digital Repository programs are supported in part by the Lowell and Eileen Aptman Digital Preservation Fund