What is a Primary Source?
Each academic discipline creates and uses primary and secondary sources differently. The definition of a primary source only makes sense in the context of a specific discipline or field of inquiry.
- In the humanities and the arts, a primary document might be an original creative work.
- It might be a part of the historical record written about, or in proximity to, an event.
- In the social sciences, it might be survey data.
- In the sciences, it might be a publication of original research.
Here are two definitions that try to capture the elusive nature of primary documents.
A definition from Cornell University: "Primary sources are the main text or work that you are discussing (e.g. a sonnet by William Shakespeare; an opera by Mozart);
actual data or research results (e.g. a scientific article presenting original findings; statistics);
or historical documents (e.g. letters, pamphlets, political tracts, manifestoes)."
["What is a Source?" Recognizing and Avoiding Plagiarism. Cornell University. College of Arts and Sciences.]
A definition from Yale University: "A primary source is firsthand testimony or direct evidence concerning a topic under investigation. The nature and value of a source cannot be determined without reference to the topic and questions it is meant to answer. The same document, or other piece of evidence, may be a primary source in one investigation and secondary in another. The search for primary sources does not, therefore, automatically include or exclude any category of records or documents."
[Yale University Library. Primary Sources Research Colloquium in History.]
A Photograph Can be a Primary Source

Antietam, Md. President Lincoln with Gen. George B. McClellan
and group of officers. [October 3, 1862]
Gardner, Alexander, 1821-1882, photographer.
Source: Library of Congress, Prints & Photographs Division
[reproduction number LC-B8171-7951]
About this photograph
Online Collections of Primary Sources: Examples
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American Memory: Historical Collections for the National Digital LibraryWashington: Library of Congress, National Digital Library Program, 1994- .
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History: Primary SourcesDatabases. Cornell University Library.
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Making of America: the Cornell University Library MOA collectionIthaca, NY: Cornell University Library, 1996- .