In 1985, the Darwin Correspondence Project produced its first publication, A Calendar to the Correspondence of Charles Darwin: 1821 – 1882 (New York: Garland), a substantial book containing a detailed summary of every letter Darwin was then known to have sent or received. That edition is no longer in print, but a revised and updated edition was published by Cambridge University Press in 1994 and the entries in that form the basis for the letter-entries on this website. The printed Calendar is still a standard reference work for Darwin scholars.
In 1996 a separate calendar was published pulling together the details of Darwin’s correspondence with German naturalists (Charles Darwins Briefwechsel mit Deutschen Naturforschern, Marburg: Basilisken-Presse).
The introductions to the printed versions of the Calendar give a good insight into the process of collecting and organising the wealth of Darwin correspondence. An article on editorial policy and practice, based on the introduction to the second edition of the Calendar, is available here.
In 2002, the Project made a fully revised version of the Calendar available online. All the information from that version, now supplemented by full transcripts of many of the letters, is available through this site. The letter descriptions are updated periodically to include new entries as letters come to light, or when research suggests a change in the dating or attribution of a letter.