Primary vs. Secondary Sources: How Historians Tell Them Apart

Every history book, documentary and museum label rests on a chain of evidence. Somewhere near the start of that chain is a letter, a ledger, a photograph or an object made by people who were there. Further along are the historians, journalists and teachers who read that material and explained what it meant.

Telling those two kinds of material apart is the first skill anyone learns when they start doing history seriously. It sounds simple, and the basic definitions are. The interesting part is that the line moves depending on what you are trying to find out.

This guide covers the standard definitions, the gray areas, and how to use both kinds of source together without being misled by either.

What makes a source primary

The Library of Congress describes primary sources as "the raw materials of history — original documents and objects that were created at the time under study." The Society of American Archivists (SAA), in its Dictionary of Archives Terminology, defines a primary source as material that contains firsthand accounts of events and that was created at the time of those events, or later recalled by an eyewitness.

The SAA dictionary's list of typical examples is a useful checklist:

• letters and diaries
• government, church and business records
• oral histories
• photographs, motion pictures and videos
• maps and land records
• blueprints

Newspapers are a classic borderline case. The SAA notes that newspaper articles written at the time of the events they describe are traditionally treated as primary sources, even though the reporter may have pieced the story together from witnesses rather than seeing it firsthand. Objects count too: the same dictionary notes that artifacts and specimens can be primary evidence when they are the thing being studied.

What makes a source secondary

The Library of Congress defines secondary sources as "accounts that retell, analyze, or interpret events, usually at a distance of time or place." The SAA describes a secondary source as a work that is not based on direct observation of, or evidence directly connected to, its subject, but instead relies on other sources of information.

Most of what people read about history is secondary: scholarly books and articles, biographies, textbooks, documentaries and encyclopedia entries. The American Historical Association (AHA), in its Statement on Standards of Professional Conduct, uses the term "secondary literature" for all later interpretations of a past period that are based on the evidence in primary documents.

Secondary does not mean second-rate. A good secondary work has done the slow labor of finding, comparing and contextualizing hundreds of primary sources, and its notes tell you where to look next.

It depends on your question

The most important idea here comes from the Guidelines for Primary Source Literacy, approved in 2018 by the SAA and by the Association of College and Research Libraries (ACRL), whose Rare Books and Manuscripts Section helped write them. They state that what makes a source primary "relies on the research question at hand," varies by discipline, and depends on how it relates to secondary sources.

A hypothetical example shows why. Imagine a high school history textbook printed in 1925 that describes the American Civil War. If your question is "what happened at a particular battle in 1863?", that textbook is secondary: it was written decades later by someone retelling other people's accounts. But if your question is "how were American students taught about the Civil War in the 1920s?", the same textbook becomes a primary source. It is a direct product of the time and practice you are studying.

Memoirs raise a related issue. Because the SAA definition includes accounts "later recalled by an eyewitness," a veteran's memoir written forty years after a war is still a primary source for that war. It is simply a distant one, shaped by memory and by everything the author read and heard in the meantime. The same is true of oral history interviews; see our guide to oral history for how historians handle that.

Copies, transcriptions and translations

You will rarely hold the original. Most people meet primary sources as digitized images, printed editions, excerpts in a textbook, or translations. The SAA and ACRL guidelines point out that a primary source can exist in many versions, including excerpts, transcriptions and translations, and they use the word "surrogate" for a copy made to stand in for an original, often to protect it from overuse.

Surrogates are enormously useful, but each step away from the original adds a layer of human choice. A transcriber may misread a word. An editor may modernize spelling or cut passages that seemed dull. A translator chooses one meaning among several. Practical habits help:

• When an edition or transcription is your main source, find out who made it and when.
• Compare a key passage against an image of the original if one exists.
• Note in your own records whether you saw the original, a facsimile, or a transcription.

Primary does not mean true

Firsthand sources feel authoritative, and that is exactly why they need care. The SAA dictionary quotes a 2001 passage on this point: primary sources "are the subjective interpretations of another person's observation of an event or activity," and many historians see it as their duty to approach them "with a healthy skepticism."

The Library of Congress makes a similar point for teachers: primary sources are "often incomplete and have little context." It suggests questions worth asking of every source, including what the creator's purpose was, who the intended audience was, and what biases or stereotypes appear in it. A diary may have been written to be read by family. A government report may have been written to justify a budget. Neither is useless; both need to be read with their purpose in mind.

Using both kinds together

In practice, historians move back and forth. A common workflow looks like this:

1. Start with a reliable secondary work to learn the basic chronology, the main people involved, and what historians have argued.
2. Follow its notes to the primary sources it relied on, and look for others it did not use.
3. Read the primary sources closely, asking who made them, when and why.
4. Return to the secondary literature to see whether your reading agrees with others or challenges them.

The AHA describes this cycle in its standards statement: historians "honor the historical record," but its interpretation "constantly evolves as historians analyze primary documents in light of the ever-expanding body of secondary literature that places those documents in a larger context." That is why history books on the same subject keep being written. New sources surface, new questions get asked, and old sources get read in new ways.

Key takeaways

• Primary sources were created at the time under study or by eyewitnesses; secondary sources retell and interpret, usually from a distance.
• Whether a source counts as primary depends on your research question, so the same book can be either.
• Copies, transcriptions and translations are useful but add layers of human choice; know which version you are reading.
• Primary sources are evidence, not verdicts: ask about purpose, audience and bias.
• Good research moves back and forth between primary and secondary sources.

Sources

• Library of Congress, Getting Started with Primary Sources
• Society of American Archivists, Dictionary of Archives Terminology: primary source
• Society of American Archivists, Dictionary of Archives Terminology: secondary source
• SAA and ACRL/RBMS Joint Task Force, Guidelines for Primary Source Literacy (June 2018)
• American Historical Association, Statement on Standards of Professional Conduct