Chicago Style Footnotes Explained

Chicago style's footnote system does something the other major citation styles don't: it lets you add genuine context, an aside, a related source, a clarifying note, without interrupting your main sentence with a parenthetical citation. That's precisely why it's the preferred system in history and several humanities fields, where a footnote can carry real analytical weight of its own.

A footnote citation appears as a small superscript number at the end of the sentence it supports, corresponding to a note at the bottom of the page (or, in the alternate endnote format, at the end of the chapter or document) with the full source information. The first full citation for a source includes complete details, author, title, publisher, year, page number, while subsequent citations of the same source can use a shortened form, just the author's last name and page number, once the full citation has already appeared once in the document.

Notes and Bibliography vs. Author-Date

Chicago actually offers two distinct citation systems, and it's important to know which one your assignment expects. The notes-and-bibliography system, described above, is standard in history and the arts. The author-date system, closer in structure to APA, is more common in the physical, natural, and social sciences when a discipline still prefers Chicago's specific style guide over APA's. The Chicago Manual of Style's citation guide covers both systems side by side, and confirming which one your assignment or publisher expects matters as much as getting the individual citation format right.

A Mini Scenario

You're citing a website in Chicago's notes system, something the standard system doesn't always handle intuitively for students used to books and journal articles. The footnote generally includes the author (or site name if no author is listed), the page or article title in quotation marks, the site name in italics, the publisher if different from the site name, the publication or last-modified date, and the URL. This is one of the more commonly mishandled entry types, since students often drop the access date or the site name, both of which Chicago typically expects for web sources specifically.

Building the Bibliography

Alongside footnotes, Chicago's notes-and-bibliography system also requires a full bibliography at the end, alphabetized by author, formatted slightly differently from the footnote entries (author's last name first, for alphabetization, and periods rather than commas separating major elements). Both the footnotes and bibliography are required together; footnotes alone, without a corresponding bibliography, don't fully satisfy Chicago's citation requirements in most academic contexts. UNC's writing resources are worth checking too if you're integrating footnoted Chicago-style research into a broader piece of academic prose, since the formatting conventions around quoting and paraphrasing still apply regardless of which citation system carries the actual source information.

Why This System Persists

Despite being more labor-intensive than a simple author-date parenthetical, Chicago's footnote system remains popular specifically because it separates a reader's two different needs, following the argument, and checking a source, without forcing either one to interrupt the other on the main page. If your discipline occasionally expects Chicago's alternate author-date format instead of full footnotes, it's worth confirming which version applies before you build an entire paper around the wrong one, and comparing Chicago's approach to APA's or MLA's author-date systems can help clarify which structure you're actually being asked to follow. Scribbr's guide to Chicago style is another useful secondary reference for the specific formatting details this article doesn't have room to cover in full.