Primary, Secondary, Tertiary, Oh My!

08.14.25 07:42 PM - By Claire B.

Historians use different types of sources to make sense of the past.  Variety is the spice of life, but it can be more than a little mind-boggling to keep them straight.  You are in the right spot if you're not sure what sources are, let alone why there are soooo many of them in your AP history class.


Read on for everything you need to know about the three main sources you'll see in your class!

What Is A Source?  

How Historians Use Sources

The job of a historian is to make sense of the past. 


First, they have to determine what happened during events.  This may seem basic, but it can be a challenge.  After all, historians usually don't live through the events they study.  So they have to gather evidence from people who did.


Second, they have to make sense of their evidence.  Historians don't just describe what happened.  They also make arguments about the past.  They may explore the relationship between events, the significance of a particular moment, or how two things are similar to each other.


It's important that these arguments are backed up by evidence.  Often history seems removed from day-to-day life.  Sometimes, that's an extremely fair criticism. 


Whatever historians are doing, it's important that these arguments are factually and logically sound.  This is where sources come in.  Like lawyers arguing a case, historians call witnesses and technical experts to the stand to testify.  If they do this well, then they create a powerful argument that reveals truth and light.  This is the foundation of all good historical communication.  

How AP History Students Use Sources

In AP history classes, you have to learn to do the work that a historian does.


This includes all sorts of fun things!

  • Develop arguments that show causation, change over time, and similarities between historical events.
  • Use evidence to prove your arguments are based in history and logical.
  • Analyze the background of your text to strengthen your argument.
  • Cite the sources you've used to develop your arguments.

This means that you also need to be familiar with different kinds of sources and how to make sense of them.  It's much easier to do this effectively if you understand the different types of sources.  

A Word on Words

Some AP history texts and teachers use different words to describe sources.  You may hear people reference the following terms:

  • Stimuli or stimulus.  This is common when discussing the Multiple Choice Questions.
  • Documents.  For example, a Document-Based Question is a type of question in AP history courses.

In the context of AP history classes, these terms are all referring to the same thing.  That is, some sort of tangible evidence that could be used to support a historical argument.  You can use them interchangeably.

I will use source throughout this article for clarity.

The other thing to note about terms is that there is subjectivity in determining what is a primary, secondary, or tertiary source.  I have included examples that I hope best represent the spirit of these categories.  But there will always be grey area between categories.  This is particularly true the further you go back in history.  The older a document is, the more likely its own background is blurry.  And, there's a long tradition of historians mixing their own lived experience with accounts from others.

Like many things in history, discretion is required.  

Primary Sources  

Definition

Often, historians decide what to study before they look for sources.  They will decide on a specific time period and place that interests them.*


A primary source is any source that is created in the time period the historian wants to study.  Typically, primary sources also come from the place the a historian wishes to study.


Any source that is faithful replication of a primary source is also a primary source.  A primary source that is translated, transcribed, recorded, photographed, quoted, or photocopied is still a primary source.


*Sometimes, historians reverse this process.  They may find a primary source that interests them and then decide to study the relevant period of time.  

A Courtroom Metaphor

Historians use sources to prove arguments.  They're hoping to show that there is a particular relationship between two events or periods of time.  This is known as a historical argument, and it must be supported by evidence.


Everyone loves a good courtroom drama.  It's also a useful metaphor for these different types of sources.


Let's say we have the classic set up.  An attorney is trying to prove that Sally stole a car.  This is the argument that the attorney will make in court.  They also need to find evidence that supports their claim.


Attorneys use eyewitness evidence to support their arguments.  For example, the owner of the stolen car may testify during the trial.  If the owner says Sally stole the car, that is very convincing evidence.


The attorney may also use photographic or video evidence.  For example, security camera footage may show Sally breaking the car's windows.


Attorneys build a strong case by having multiple pieces of high-quality evidence.  Evidence from people (or cameras) that were at the scene of the crime are very compelling.  


The same is true for historians.  High-quality primary sources help create a convincing argument.  

Examples

Historians have a LOT of options when it comes to primary sources.  Here are some things that are often primary sources.

  • Letters
  • Memoirs and Autobiographies
  • Photographs
  • Video and Audio Recordings
  • Posters
  • Newspaper Articles
  • Literature and Art
  • Interviews
  • Government Data

Note: Just because a source falls into one of these categories does not mean it is a primary source, or even relevant to the topic you're studying.  If you're not sure, go back to the definition.  Was this source created in the time and place you wish to study?

Still have questions about primary sources?  I have a deep dive on the subject here.  

Secondary Sources  

Definition

Secondary sources are created by studying several primary sources and drawing conclusions based on research.  Secondary sources generally focus on one or more historical arguments.  That means the writer is trying to assert that there is a specific connection between events, or that a specific trend occurred within a time period.


Secondary sources are typically made by experts in a topic.  This is often a historian, but it could be a journalist, writer, amateur historian, or any other person who has done sufficient research on the topic.  Similarly, secondary sources are often made by people who did NOT witness the events firsthand.  Their research and expertise is the basis of their credibility.  

A Courtroom Metaphor

Let's return to our courtroom example.  Sally is accused of stealing a car. 


Like before, attorneys on both sides are trying to build a strong case by citing multiple pieces of evidence.  They can make their case strong by citing different kinds of evidence.  So, in addition to the eyewitness testimony (primary source), they may also bring in experts to testify.


For example, the prosecutor may bring in an expert on fingerprinting.  The expert says that the prints on Sally's fingers match the prints found on the car's steering wheel.  


This would help support the argument that Sally stole the car.  Unlike the eyewitnesses, we don't trust this source because they saw the event happen.  The expert's testimony is credible because of their investigation into the topic and their existing expertise.  


This is like a secondary source because they aren't created by someone who saw the event.  Instead, they are created by someone whose opinion is respected because of their training and research.  

Examples

All of the following can be secondary sources:

  • Newspaper articles, especially opinion pieces.
  • Topical history books
  • Biographies
  • Interviews with experts
  • Charts, graphs, or maps based on compiled or selected data  

Tertiary Sources 

Definition

Tertiary sources summarize the factual details of history.  They are created by researching primary and secondary sources.  Then, the writer determines which facts and interpretations are generally accepted.


The biggest difference between secondary and tertiary source is the goal.  A secondary source presents a historical argument.  A tertiary source presents the basic facts of an event.  This may include the significance of the event or it's connection to other events, as currently understood by historians.  But a tertiary source isn't trying to present new research or advance its own argument.  

A Courtroom Metaphor

It's less common for tertiary sources to be cited in courtrooms, so I don't have a great metaphor here.  But even this tells us something.  Even outside of history, a source that's three steps away from the events is seen as less credible than one that's closer.  

Examples

All of the following can be tertiary sources.

  • Encyclopedia articles
  • Textbooks
  • Documentaries
  • Bibliographies
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