Complete Chicago Style Format Guide: Notes and Author-Date, 18th Edition

Chicago Style Paper Formatting Basics

Chicago Style: Two Complete Systems

Chicago offers two distinct citation systems. Pick one and use it consistently; never mix them.

1. Notes-Bibliography System

Best for: History, theology, arts, humanities

How it works:

• Superscript numbers in text¹
• Full citations in footnotes (bottom of page) or endnotes (end of paper)
• Complete bibliography at the end

Why historians prefer it: Footnotes provide source details plus commentary without cluttering the main text.

2. Author-Date System

Best for: Social sciences, natural sciences, when emphasizing publication dates

How it works:

• Parenthetical citations (Smith 2024, 45)
• Reference list at the end

Why scientists prefer it: Quick publication date visibility, similar to APA format.

This guide covers both systems. Jump to your required system below.

Notes-Bibliography System Specifications

1. Paper Setup

Formatting:

• Font: 12pt Times New Roman (or another readable serif font)
• Margins: 1 inch all sides
• Spacing: Double-space body text, single-space footnotes
• Indent: 0.5 inch first line of paragraphs
• Page numbers: Top right or bottom center

Title Page (student papers):

• Title (centered, 1/3 down page)
• Your name (centered, below title)
• Course info (centered, below name)
• Date (centered, last)

No separate title page needed for shorter papers, put title centered at top of first page.

2. Footnote Format

• In text: Place superscript number after punctuation¹
• At the bottom of the page: Footnote with full citation details

First reference to source (full format):

• Book:
  1. Jennifer Thompson, Social Movements in Modern America (Chicago: University of Chicago Press, 2023), 45.
  
  
• Journal article:
  2. Michael Chen and Lisa Rodriguez, "Urban Development Patterns," Journal of Urban History 89, no. 3 (2024): 234-56.
  
  
• Website:
  3. American Historical Association, "Research Guidelines," accessed December 20, 2024, https://www.historians.org/guidelines.

Subsequent references (shortened):
4. Thompson, Social Movements, 67.
5. Chen and Rodriguez, "Urban Development," 240.

Immediately repeated source:
6. Thompson, Social Movements, 45.
7. Ibid., 52. Same source, different page
8. Ibid. Same source, same page

3. Bibliography Format

Start the bibliography on a new page after the main text.

• Title: "Bibliography" centered at top.
  
  
• Entry format: Hanging indent, single-spaced within entries, double-spaced between entries

Alphabetize by author's last name

• Book:
  Thompson, Jennifer. Social Movements in Modern America. Chicago: University of Chicago Press, 2023.
  
  
• Journal article:
  Chen, Michael, and Lisa Rodriguez. "Urban Development Patterns." Journal of Urban History 89, no. 3 (2024): 234-56.
  
  
• Website:
  American Historical Association. "Research Guidelines." Accessed December 20, 2024. https://www.historians.org/guidelines.

Key differences from footnotes:

• Author name reversed (Last, First)
• Periods replace commas between elements
• No parentheses around publication info
• Full page range for articles

Author-Date System Specifications

1. Paper Setup

Same as Notes-Bibliography:

• 1-inch margins on all sides
• 12pt Times New Roman
• Double-space body text
• 0.5-inch paragraph indent

No footnotes for citations? Use parenthetical references instead.

2. In-Text Citation Format

• Basic citation:
  Early settlers faced numerous challenges (Martinez 2024, 112).
  
  
• Author in sentence:
  Martinez (2024, 112) documents the challenges faced by early settlers.
  
  
• Two authors:
  (Smith and Johnson 2023, 45)
  
  
• Three or more authors:
  (Rodriguez et al. 2024, 78)
  
  
• Multiple works:
  (Brown 2022; Garcia 2023; Wilson 2024)
  
  
• Page ranges:
  (Thompson 2024, 45-52)
  
  
• No page number (general reference):
  (Chen 2024)

Note: Chicago Author-Date uses a comma before the page number, unlike Chicago Notes, which doesn't.

3. Reference List Format

• Title: "References" or "Reference List" centered at top
  
  
• Entry format: Hanging indent, alphabetized by author's last name
  
  
• Book:
  Martinez, Roberto. 2024. Western Settlement Patterns. New York: Oxford University Press.
  
  
• Journal article:
  Chen, Michael, and Sarah Williams. 2024. "Migration and Identity." American Historical Review 89 (3): 456-89.
  
  
• Edited book:
  Thompson, Jennifer, ed. 2023. Essays in Modern History. Chicago: University of Chicago Press.
  
  
• Book chapter:
  Johnson, Mark. 2024. "Economic Development." In Regional Histories, edited by Lisa Chen, 123-45. Boston: Beacon Press.
  
  
• Website:
  National Archives. 2024. "Primary Source Collections." Accessed December 20, 2024. https://www.archives.gov/collections.

Chicago Citation Formats by Source Type

Books

Notes-Bibliography (footnote):

1. Rebecca Thompson, Colonial America: A Social History (Boston: Beacon Press, 2023), 67.

Notes-Bibliography (bibliography):
Thompson, Rebecca. Colonial America: A Social History. Boston: Beacon Press, 2023.

Author-Date (reference):
Thompson, Rebecca. 2023. Colonial America: A Social History. Boston: Beacon Press.

Two authors:

• Note: 2. Michael Smith and Jennifer Jones, Urban Development (New York: Norton, 2024), 45.
• Bib: Smith, Michael, and Jennifer Jones. Urban Development. New York: Norton, 2024.
• Ref: Smith, Michael, and Jennifer Jones. 2024. Urban Development. New York: Norton.

Edited book:

• Note: 3. Amanda Rodriguez, ed., Historical Perspectives (Chicago: University of Chicago Press, 2023), 89.
• Bib: Rodriguez, Amanda, ed. Historical Perspectives. Chicago: University of Chicago Press, 2023.
• Ref: Rodriguez, Amanda, ed. 2023. Historical Perspectives. Chicago: University of Chicago Press.

Translated book:

• Note: 4. Michel Foucault, Discipline and Punish, trans. Alan Sheridan (New York: Vintage, 1977), 23.
• Bib: Foucault, Michel. Discipline and Punish. Translated by Alan Sheridan. New York: Vintage, 1977.

Ebook:

• Note: 5. Sarah Johnson, Digital Archives (London: Routledge, 2024), Kindle, loc. 456.
• Bib: Johnson, Sarah. Digital Archives. London: Routledge, 2024. Kindle.

Journal Articles

Notes-Bibliography (footnote):
6. David Chen, "Industrialization and Society," Journal of American History 107, no. 2 (2024): 234-56.

Notes-Bibliography (bibliography):
Chen, David. "Industrialization and Society." Journal of American History 107, no. 2 (2024): 234-56.

Author-Date (reference):
Chen, David. 2024. "Industrialization and Society." Journal of American History 107 (2): 234-56.

Article with DOI:

• Bib: Martinez, Luis. "Economic Patterns." Historical Review 89, no. 4 (2023): 456-78. https://doi.org/10.1234/hist.2023.04.
• Ref: Martinez, Luis. 2023. "Economic Patterns." Historical Review 89 (4): 456-78. https://doi.org/10.1234/hist.2023.04.

Primary Sources

Archival material:

• Note: 7. Abraham Lincoln to Mary Todd Lincoln, April 16, 1865, Lincoln Papers, Library of Congress, Washington, DC.
• Bib: Lincoln, Abraham. Abraham Lincoln Papers. Library of Congress, Washington, DC.

Government document:

• Note: 8. U.S. Congress, Senate, Committee on Foreign Relations, Hearings on Treaty Ratification, 89th Cong., 2nd sess., 1966, S. Doc. 45, 23.
• Bib: U.S. Congress. Senate. Committee on Foreign Relations. Hearings on Treaty Ratification. 89th Cong.., 2nd sess.., 1966. S. Doc. 45.

Historical newspaper:

• Note: 9. "Treaty Signed in Paris," New York Times, June 28, 1919.
• Bib: New York Times. 1919. "Treaty Signed in Paris." June 28, 1919.

Digital Sources

Website article:

• Note: 10. Jennifer Martinez, "Digital Humanities Methods," History Today, May 15, 2024, https://www.historytoday.com/digital-methods.
• Bib: Martinez, Jennifer. "Digital Humanities Methods." History Today. May 15, 2024. https://www.historytoday.com/digital-methods.

Blog post:

• Note: 11. Michael Thompson, "Understanding Historical Context," The History Blog (blog), March 10, 2024, https://historyblog.com/context.
• Bib: Thompson, Michael. "Understanding Historical Context." The History Blog (blog). March 10, 2024. https://historyblog.com/context.

Online database:

• Note: 12. Census data, U.S. Census Bureau, American FactFinder, accessed November 20, 2024, https://factfinder.census.gov.

Common Chicago Style Mistakes

Mistake 1: Mixing the Two Systems

• Incorrect: Using footnotes AND parenthetical citations
• Correct: Pick one system, use it throughout the entire paper
• Fix: Choose Notes-Bibliography OR Author-Date. Never both.

Mistake 2: Wrong Footnote Punctuation

• Incorrect: Thompson, Jennifer, Social Movements (Chicago: University Press, 2023) 45.
• Correct: Thompson, Jennifer, Social Movements (Chicago: University Press, 2023), 45.
• Fix: Comma before page number in footnotes.

Mistake 3: Footnote Format in Bibliography

• Incorrect: Thompson, Jennifer, Social Movements (Chicago: University Press, 2023), 45.
• Correct: Thompson, Jennifer. Social Movements. Chicago: University Press, 2023.
• Fix: Bibliography uses periods, no parentheses, no page numbers for books.

Mistake 4: Wrong "Ibid." Usage

• Incorrect: Using "Ibid." when several notes separate repeated source
• Correct: Use "Ibid." only for immediately preceding note
• Fix: If any other source appears between, use the shortened form instead.

Mistake 5: Author-Date Citation Punctuation

• Incorrect: (Martinez 2024: 45) Colon like ASA
• Incorrect: (Martinez, 2024, p. 45)  APA format
• Correct: (Martinez 2024, 45) Chicago Author-Date
• Fix: Comma before page, no "p."

Mistake 6: Single-Spacing Footnotes

• Incorrect: Double-spacing footnotes like body text
• Correct: Single-space within footnotes, double-space between them
• Fix: Format footnotes differently from the main text.

Mistake 7: Not Reversing Author Names in Bibliography

• Incorrect: Jennifer Thompson. Social Movements.
• Correct: Thompson, Jennifer. Social Movements.
• Fix: Last name first in bibliography/reference list.

Mistake 8: Missing Access Dates for Websites

• Incorrect: No access date for online sources
• Correct: "Accessed December 20, 2024" for websites
• Fix: Include the access date, especially for sources that may change.

Chicago vs Other Styles

For a Complete overview, refer to the Citation Styles guide for details on different citation styles and their applications.

Chicago Style 18th Edition Updates

The 18th edition (2024) introduced several changes:

Digital source improvements:

• Clearer guidance for social media
• Better streaming content formats
• Updated database citation rules

Author-Date enhancements:

• Simplified multiple author handling
• Clearer DOI formatting
• Better integration with online sources

Notes-Bibliography refinements:

• Streamlined "Ibid." usage
• Improved archival citation formats
• Better handling of unusual sources

General updates:

• Gender-neutral language guidance
• Accessibility considerations
• Modern publication format handling

Still using the 17th edition? Update to 18th: many instructors now require it.

Free Downloadable Resources

Chicago Notes-Bibliography Template
Pre-formatted document with footnotes set up

Chicago Author-Date Template
Pre-formatted with parenthetical citation setup

Chicago Citation Quick Reference
One-page guide for both systems

Footnote vs Bibliography Format
Side-by-side comparison chart

Chicago Format Checklist
Pre-submission verification list

Master Chicago Style

Chicago style's flexibility, offering both Notes-Bibliography and Author-Date systems, makes it adaptable across disciplines. Choose Notes-Bibliography for history and humanities, where footnote commentary adds value. Choose Author-Date for sciences where publication dates matter most.

Most mistakes come from mixing the two systems or applying APA rules to Chicago. Use this guide as a reference, pick your system early, and apply it consistently throughout. For a full understanding of all citation styles, check out our citation styles guide.