Primary and secondary sources, with examples from every era
6 min read
A primary source was made at the time you are studying, or by someone who took part: a letter, diary, speech, photograph, law or object. A secondary source was made later by someone interpreting primary sources, such as a biography or a history book. A tertiary source, like an encyclopedia or textbook, summarises secondary sources. The same item can be primary or secondary depending on your question.
The definitions, in one table
| Primary | Secondary | Tertiary | |
|---|---|---|---|
| Made | At the time, or later by a witness | Later, by someone studying the past | Later, summarising other work |
| Examples | Letters, diaries, speeches, laws, photos, maps, objects, interviews with witnesses | Biographies, history books, journal articles, documentaries | Encyclopedias, textbooks, timelines, study guides |
| Gives you | Evidence | Interpretation and argument | A quick overview |
| Main risk | Bias, gaps, a narrow view | The author's argument and choices | Simplified, often uncited |
Historians build arguments from primary sources and test them against secondary ones. A good school project uses both, and uses tertiary sources only to get started.
Examples from each era
| Era | Primary source | Secondary source |
|---|---|---|
| Ancient Greece | Plato's Apology, his account of Socrates's trial in 399 BCE | A modern history of Athens |
| Ancient India | Ashoka's rock and pillar edicts, 3rd century BCE | Romila Thapar, Aśoka and the Decline of the Mauryas (1961) |
| Medieval England | Domesday Book (1086), the survey ordered by William the Conqueror | David Bates, William the Conqueror (2016) |
| Scientific Revolution | Galileo's Sidereus Nuncius (1610), his drawings of the Moon | A biography of Galileo |
| American Revolution | Abigail Adams's letter to John Adams, 31 March 1776 | A study of women in the Revolution |
| Abolition | Frederick Douglass's Narrative (1845) | David Blight, Frederick Douglass: Prophet of Freedom (2018) |
| Victorian Britain | Florence Nightingale's polar-area diagram of army deaths (1858) | A history of the Crimean War |
| Early 20th century | Marie Curie's laboratory notebooks, still radioactive and kept in protective boxes in Paris | Susan Quinn, Marie Curie: A Life (1995) |
Tertiary sources, and where they fit
Encyclopedias (Britannica, Wikipedia), textbooks, study guides and timelines are tertiary sources. They are good for a first look: dates, names, the shape of a life. They are not evidence. Most teachers will not accept them in a bibliography, or accept them only alongside better sources.
Use a tertiary source to find what to look for, then follow its references. A Wikipedia article's footnotes often lead you to the biography or the archive you actually need.
The tricky cases
Whether something is primary depends on the question you are asking, not on the object itself.
- A newspaper from 1863 is primary for 1863. A newspaper article from 2013 about 1863 is secondary. That same 2013 article would be primary if your project were about how the anniversary was remembered in 2013.
- An autobiography is primary, but written later. Douglass described his escape of 1838 only in 1881, and memories shift. Note the gap.
- Someone else's account of a person can be a primary source for them. Socrates wrote nothing; what we know comes from Plato, Xenophon and Aristophanes, who knew him. They are primary sources, but each had their own aims.
- A biography written by a contemporary can be both. Sarah Bradford's books on Harriet Tubman (1869 and 1886) record Tubman's words, but Bradford also shaped and exaggerated them.
- A translation is still the primary source, but the translator made choices. For an important passage, compare two translations.
- A museum label or documentary is secondary. A photograph or interview inside the documentary may be primary.
Where AI chatbots fit
An answer from an AI chatbot is not a primary source about the past. It was made now, by a program, from a mix of texts it cannot reliably name. It is not a dependable secondary source either, because it does not show its evidence and can invent details or quotations. Treat it as a starting point, like a conversation, and then find the real source.
That includes AI recreations of historical figures. On Yuga, for example, you can ask Abigail Adams about her letters by voice or text, and the app marks which lines are drawn from her writing. That is a useful way to find where to look. What you cite is the letter itself. Our guide using AI to study history covers the rules most teachers set.
How teachers grade the use of sources
Teachers rarely give marks just for listing primary sources. They give marks for what you do with them. Most mark schemes, from middle school projects to the AP and IB exams, reward four habits that the education researcher Sam Wineburg called reading like a historian:
- Sourcing: who made this, when, and why? A letter written to persuade is different from a private diary.
- Contextualisation: what was happening at the time that shaped the source?
- Corroboration: do other sources agree? Where they disagree, which is more reliable, and why?
- Close reading: what words did the author choose, and what did they leave out?
In the AP history Document-Based Question, scored out of 7 points, one point goes for sourcing: explaining, for at least two documents, how the author's point of view, purpose, historical situation or audience matters to your argument. The IB asks for the same thing as OPCVL (origin, purpose, content, value, limitation). For a full method with a worked example, see how to analyze a primary source.
A quick checklist for any source
- When was it made, and how long after the events?
- Who made it, and were they there?
- Who was it made for?
- Why was it made: to inform, persuade, remember, record?
- What can it tell you, and what can it not?
- Is it the original, a copy, an edition or a translation?
- Can you find a second source that agrees?
If you need places to find primary sources online for free, start with the list of free primary source archives.
Questions people ask
- What is the difference between a primary and secondary source?
- A primary source was created at the time being studied or by someone who was there, such as a letter, diary, speech or photograph. A secondary source was created later by someone interpreting primary sources, such as a biography or history book. Primary sources give evidence; secondary sources give interpretation.
- Is a newspaper a primary or secondary source?
- It depends on your question. A newspaper report from the time of an event is a primary source for that event. An article written decades later about the event is secondary. Even an old newspaper is secondary if it describes events from long before it was printed.
- Is an autobiography a primary source?
- Yes. It is the person's own account of their life. But it was usually written years after the events, often to make a case, so check it against letters or records from the time. Frederick Douglass published three autobiographies, in 1845, 1855 and 1881, and they differ in detail.
- Is a textbook a secondary or tertiary source?
- Usually tertiary. A textbook summarises the work of historians rather than making its own argument from primary sources. Encyclopedias, including Wikipedia, are tertiary too. They are useful for a first overview and for their references, but teachers expect you to go further.
- Is an AI chatbot a primary source?
- No. A chatbot's answer is generated today from many texts it cannot reliably name, and it can be wrong or invent quotations. Use it to get ideas or find what to search for, then find and cite the actual document or a published history.
Sources
- Sam Wineburg, Historical Thinking and Other Unnatural Acts (2001)
- National Archives, DocsTeach: primary source activities
- Library of Congress, Teaching with Primary Sources
- College Board, AP United States History Course and Exam Description (DBQ rubric)
- Romila Thapar, Aśoka and the Decline of the Mauryas (1961)