How to Cite a Letter

Letters are among the most rewarding primary sources and the most fiddly to cite, because their accessibility varies so much. A letter in a catalogued archive is fully citable. A letter in your own inbox is not. That distinction, not the letter's age, drives the format.

Three Categories

Published letters appear in edited collections, scholarly editions and biographies. Cite the collection.

Archival letters are unpublished documents held in a library, museum or archive. They get a full reference, with enough finding-aid detail to locate the item.

Private correspondence — a letter or email sent to you — is a personal communication.

Published Letters

When a letter appears in an edited collection, cite it as you would a piece in an edited book.

APA:

A real collection, verified in a library catalogue:

MLA:

Chicago (18th Edition, Notes–Bibliography) treats it as a part of an edited book. Its Citation Quick Guide gives this pattern for a chapter or other part of an edited book, noting that the page range is no longer required in the bibliography but specific pages are cited in a note:

If the letter has an editorial title, use it. If not, describe it — "Letter to Thomas Jefferson, 15 July 1813" — rather than inventing one.

Archival Letters

APA publishes a full set of archival formats, and the guiding principle it states is the useful one: "Include as much information as is needed to help locate the item with reasonable ease within the repository. For items from collections with detailed finding aids, the name of the collection may be sufficient; for items from collections without finding aids, more information (e.g., call number, box number, file name or number) may be necessary to help locate the item."

Key elements: author, recipient, date, a description if there is no title, the collection name, finding-aid details, and the repository with its location.

APA's own published example of a letter from a repository:

Because the letter has no title, the description goes in square brackets — APA's rule is to italicize titles of archival documents, and to give an unitalicized bracketed description when there is no title.

APA's example of a whole run of correspondence cited as one reference:

with individual letters identified in the in-text citation:

And, for a letter in someone's private collection, APA's example — which only works where the collector has agreed:

Chicago's archival pattern runs author to recipient, date, collection, finding-aid details, repository, city. Here it is applied to a letter whose archival details were verified against the digital edition that publishes it:

That letter is catalogued by the Darwin Correspondence Project as letter no. DCP-LETT-2143; the project records its source of text as "Imperial College of Science, Technology, and Medicine Archives (Huxley 5: 54)", describes it as an autograph letter signed of seven pages, and notes that it is also published in The Correspondence of Charles Darwin, volume 6. Where a digital edition like this exists, citing both the manuscript location and the edition's stable link is the most useful thing you can do for a reader:

The project publishes its own "Please cite as" form for each letter, and it asks for an access date:

Private Correspondence

A letter or email sent to you is cited in the text only. APA's instruction is to "give the initial(s) and surname of the communicator, and provide as exact a date as possible", and its published examples of the form are:

Filled in for your own correspondence:

Chicago's own note example covers the same ground for messages:

MLA covers unpublished correspondence in the MLA Handbook (9th ed.) rather than on the free MLA Style Center, so check the Handbook or your library's MLA guide before building a works-cited entry for a letter your reader cannot obtain.

The reasoning behind all three: readers cannot check private correspondence, so it does not belong in a list of works they could consult.

Email and Other Messages

Email follows the personal-communication rule when it is correspondence with you. APA's list of personal communications includes emails, text messages, online chats and direct messages.

Email that has been published or made public — in a published edition, a court exhibit, a records release or an institutional archive — stops being a personal communication and is cited as the published or archival document it has become. APA says as much for archives generally: material "recoverable only in an archive" is cited as archival material, not as a personal communication.

Historical vs. Contemporary Letters

The distinction is not age, it is accessibility. A 1950 letter catalogued in a university archive gets a full reference. A letter your supervisor sent you last week does not, whatever its content.

The corollary is worth knowing: if you deposit your own correspondence in an archive, it becomes citable. Until then, APA notes that authors "may choose to list correspondence from their own personal collections", while correspondence from someone else's private collection needs the collector's permission.

Permissions

For archival material, follow the repository's stated terms for citation, quotation and reproduction; they are normally in the finding aid or the reader agreement.

For private correspondence, get the writer's agreement before quoting at length, and think about whether the content is sensitive before quoting at all. For someone else's private collection, APA requires the collector's permission.

Formatting the Date

Give as much of the date as the document supports:

• Full date: 15 March 1842
• Partial: March 1842, or Spring 1842
• Estimated: APA's archival rule is to "use 'ca.' (circa) to indicate an estimated date" — ca. 1842
• Conjectural, supplied by you: [1842?] in square brackets, since APA reserves brackets for information not on the document
• Unknown: n.d.

Multiple Letters Between the Same Parties

APA's rule: "If several letters are cited from the same collection, list the collection as a reference and provide specific identifying information (author, recipient, and date) for each letter in the in-text citations" — the Allport pattern above. That keeps the reference list short and each in-text citation precise.

Letters in Digital Archives

Many archives have digitized correspondence with stable URLs, as the Darwin Correspondence Project does. Where the link is stable, give it alongside the manuscript details:

If the archive requires a login or its links are session-based, cite the physical collection details instead, and note the digital edition by name.

Where These Rules Come From

• APA: the "Archival Documents and Collections" page and the "Personal Communications" page on the APA Style site (apastyle.apa.org). APA's own note on the archival page is that this content "is available only on the APA Style website" and is not in the Publication Manual or Concise Guide; personal communications are covered in Section 8.9. APA's site refuses automated requests, so both were read through dated Internet Archive captures (30 June and 30 August 2026), and every APA example and quoted sentence above comes from them.
• APA, corroborated: Murdoch University Library's APA 7th guide and James Cook University Library's APA guide, "Personal Communication" (libguides.murdoch.edu.au/APA/personal, libguides.jcu.edu.au/apa/personal-communication), read live.
• Chicago: the free Chicago Manual of Style 18th-edition Citation Quick Guide, "Chapter or other part of an edited book" (CMOS 14.8–14) and "Personal communication" (CMOS 14.111), read live — the Sam Gomez note and the rule that personal communications "are usually cited in the text or in a note only; they are rarely included in a bibliography" are quoted from it.
• The Cappon edition was checked against Open Library's catalogue record (openlibrary.org/books/OL13528159M): The Adams-Jefferson letters: the complete correspondence between Thomas Jefferson and Abigail and John Adams, "Edited by Lester J. Cappon", published 1959 at Chapel Hill for the Institute of Early American History and Culture at Williamsburg, Va., by the University of North Carolina Press. The Darwin letter was checked against the Darwin Correspondence Project's record for DCP-LETT-2143, which gives "To T. H. Huxley 26 September [1857]", source of text "Imperial College of Science, Technology, and Medicine Archives (Huxley 5: 54)", physical description "ALS 7pp", the project's own recommended citation form, and "Also published in The Correspondence of Charles Darwin, vol. 6".