In the previous post, I discussed the benefits and drawbacks of Wikipedia. In this post, we’ll do a quick examination of the different types of sources as they relate to doing historical research.

Primary vs. secondary vs. tertiary sources in the field of history

There are three basic types of sources used in historical research. These are primary, secondary, and tertiary sources.

What is a primary source?

A primary source is something from the era that you are researching. These could be things like newspaper or magazine articles, letters, diaries, government reports, archival documents, emails, audio/video recordings, music, oral histories, physical artifacts, etc. For example, a propaganda poster is a primary source from the era during which it was created.

What is a secondary source?

A secondary source reports on, analyzes, summarizes, or distills information from primary sources. For example, Thomas Jefferson’s autobiography is a primary source because it’s his firsthand account of his life. In contrast, a biography of Thomas Jefferson is a secondary source because it relies on other sources (and probably the autobiography) to report on and interpret the life of Thomas Jefferson. Another example of a secondary source might be an article written in a scholarly journal on the topic of propaganda posters from WWII.

Published vs. unpublished primary sources

Published primary sources are books or periodicals that were widely distributed during that time period.

Unpublished primary sources are documents, emails, archived sources, manuscripts, or stuff that otherwise doesn’t get a wide and public distribution. They are usually more difficult to find. An example of a published primary source would be a newspaper article from July 1, 1900, while a personal letter written on that same day would be an unpublished primary source.

One thing to note is that the line between primary and secondary source is not always hard and fast. Say I’m doing a study on 19th century textbooks and social studies education, and I find a history textbook from that era. The textbook is technically a secondary source on the subject of history, however, for the purposes of my study, it serves as a primary source because it’s from that era and it relates to my topic of study.

What is a tertiary source?

Tertiary sources are places where information is heavily consolidated. Encyclopedias, dictionaries, almanacs, atlases, indexes, etc. qualify as tertiary sources.

Examples of tertiary sources might include Wikipedia, a National Geographic Atlas, and the Guinness Book of World Records.  

Some secondary sources can also be tertiary sources. Tertiary sources are generally not used in academic research unless they can be also used as secondary sources.

As a general guiding principle, primary sources are preferred over secondary sources, and secondary sources are preferred over tertiary sources in research. That being said, if it comes down to the matter of using a tertiary source or no source at all, then obviously a tertiary source is preferred. In fact, any source is better than no source, and tertiary sources are probably better than your average website published by JoBlo.


Stebbins, L.F. (2006). Student Guide to Research in the Digital Age: How to Locate and Evaluate Information Sources. Westport, CT: Libraries Unlimited.