- 1913 to 19142,672
- 1915 to 19197,482
- 1920 to 19246,656
- 1925 to 19295,070
- 1930 to 19344,083
- 1935 to 19395,819
- 1940 to 19445,464
- 1945 to 194910,127
- 1950 to 195410,151
- 1955 to 19597,518
- 19607,875
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