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Understanding Historical Sources: Home

A guide to primary, secondary, and tertiary sources in history.

Charles Conrad reflected in Alan Bean's visor during Apollo 12 lunar landing, 1969

Primary Sources

Primary sources are documents, objects, or images created at the time of the event; they provide firsthand accounts or evidence of the time period you are studying. 

Examples of primary sources are such things as:

  • The diary of a person living through the event, such as Anne Frank's original diary

  • A photograph of the event, such as the famous "Migrant Mother" photo taken by Dorothea Lange

  • A document produced at the time, like the Declaration of Independence

  • Newspaper accounts written at the time in question

  • Data sets such as surveys or a census

  • A recording of an oral history given by your grandmother

  • Letters, such as John and Annie Bidwell's correspondence

  • A piece of pottery made by ancient peoples

  • A quilt made in 1920 at Gee's Bend, Alabama

Primary sources allow researchers to get as close to the event as they can.

Digital representations of primary sources are scattered across the internet, often in specialized collections.  Below are a few examples:

"Migrant Mother" photo by Dorothea Lange.

The migrant worker woman pictured, Florence Owens Thompson, had this photo taken in Nipomo.  She spent some of her early years in Oroville.

Secondary Sources

Secondary sources are a step removed from the primary sources they use as material.  They describe, analyze, or interpret the historical events for the reader.  A historian or archeologist studies primary sources and then makes interpretations, synthesizing the information for the reader.  Of course, our knowledge of history is always incomplete and imperfect, and is also always being refined and reinterpreted.  Thus our ideas about virtually any historical event are now very different than they were 100, 50, or even 20 years ago. 

Examples of secondary sources include:

  • Almost any book about a historical event that was not written at the time
  • Analysis of a data set, such as a census
  • A scholarly article giving a new interpretation of an event
  • A documentary about the Civil War (which will show images of primary sources, but will mostly provide description and commentary)
  • An informational station at a museum which interprets the primary sources shown

The Butte College Library is filled with secondary sources -- which often feature transcriptions or images of primary sources as evidence.  Search for books on your topic by entering a descriptive term into the Library's search box, for example:


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Rachel Arteaga

Tertiary Sources

Tertiary sources mostly tell you where to find primary and secondary sources; they summarize and direct the researcher to resources.  Tertiary sources include:

  • Bibliographies -- lists of books about a particular topic
  • Encyclopedias or other reference works
  • Indexes -- lists of topics and where to find more information on them
  • Abstracts -- short summaries of articles or books on a topic

Use tertiary sources to locate what you are looking for and to make sure that you have found the best information available.  Some example of tertiary sources include:


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Jean Ping