The Mainz City Library preserves an extensive collection of medieval manuscripts and old prints as part of its historical heritage. Remarkable special collections, such as the output of the children's book publisher Jos. Scholz, Jakob Moyat's ornithological book collection, and the Peter Cornelius Archive, grew out of donations and bequests, which were supplemented by antiquarian acquisitions.

As a vibrant research institution, the City Library provides current literature for working with its manuscripts, historical prints, autographs, bequests, and special collections. Some of this literature can be found in a separate open-access area on the first floor of the library (access via the lending desk).