- 1910 to 19143,571
- 1915 to 19197,478
- 1920 to 19246,652
- 1925 to 19295,066
- 1930 to 19344,082
- 1935 to 19395,817
- 1940 to 19445,462
- 1945 to 194910,127
- 1950 to 195410,151
- 1955 to 19597,517
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