- 1880 to 18893,442
- 1890 to 18994,182
- 1900 to 19094,400
- 1910 to 19199,316
- 1920 to 192910,061
- 1930 to 193910,202
- 1940 to 194915,864
- 1950 to 195914,957
- 1960 to 196922,541
- 1970 to 197914,133
- 1980 to 19824,307
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