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Source analysis: The skill of examining historical sources
Anna Kowalski
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calendar_month2026-01-28

Uncovering the Past: A Beginner's Guide to Source Analysis

Learning how to ask questions of historical evidence to separate fact from fiction.
Summary: Source analysis is the core skill of a historian, akin to being a detective for the past. It involves systematically examining historical sources—whether written documents, photographs, maps, or artifacts—to understand their meaning, judge their reliability, and determine their value for answering specific historical questions. This process relies on key techniques like contextualization, corroboration, and critical thinking, moving us beyond simply accepting information at face value to constructing informed and nuanced interpretations of history.

The Detective's Toolkit: Core Principles of Source Analysis

Every piece of historical evidence is a clue. To solve the mystery of "what really happened," historians use a set of foundational principles. Think of these as the magnifying glass and notebook of your historical detective kit.

The first step is to identify what type of source you are examining. This helps you understand the unique questions you need to ask. Broadly, sources are categorized as either primary or secondary.

Source TypeDefinitionExamples
Primary SourceA document, object, or other source of information created at the time under study. It is a firsthand account or direct evidence.A soldier's letter from the trenches in 1916, a photograph of a civil rights march, a coin from ancient Rome, the original text of the U.S. Constitution.
Secondary SourceA source that analyzes, interprets, or describes primary sources. It is created after the event by someone who was not present.A history textbook chapter on the Roman Empire, a biography of a president, a documentary film about World War II.

Once you have identified the source type, you begin the real investigation by asking a series of critical questions. These questions are often grouped into stages: first understanding the source's content and origin (external criticism), then probing its meaning and truthfulness (internal criticism).

Tip: The 5 Ws (and H) of Source Analysis
A simple way to remember the key questions is to adapt the journalist's checklist:

  • Who created it? (Author/Creator)
  • What is it? (Content/Type)
  • When was it created? (Date)
  • Where was it created? (Place of Origin)
  • Why was it created? (Purpose/Motive)
  • How was it created? (Method/Medium)

Asking the Right Questions: Evaluating Meaning and Reliability

This stage is where you dig deeper into the clues. You are not just collecting facts about the source; you are interpreting them to assess how useful and trustworthy the source is. This involves three interconnected concepts: Context, Corroboration, and Bias.

Context is everything. A source cannot be understood in isolation. You must place it back into its historical setting. For example, a political cartoon mocking a king makes much more sense when you know the specific laws he passed that angered the people. Asking "What was happening at this time and place?" is essential.

Corroboration means checking the information against other sources. No single source tells the whole story. If a diary entry claims it rained on the day of a famous battle, you would look at other diaries, official weather records, or letters from the same day to see if they mention the rain. When multiple independent sources agree, the information is more reliable. This can be thought of as a simple formula for historical certainty:

$Reliability \propto \frac{Number\ of\ Corroborating\ Sources}{Independence\ of\ those\ Sources}$

Where the symbol $\propto$ means "is proportional to." More corroborating sources increase reliability, but only if they are truly independent and not just copying from one another.

Bias is a predisposition for or against something. Every source has a point of view, shaped by the creator's background, beliefs, and purpose. Identifying bias is not about dismissing a source as "bad." It's about understanding the lens through which the information is filtered. A newspaper article from a pro-government paper and one from an opposition paper about the same protest will highlight different facts and use different language. Your job is to identify that bias and consider how it affects the source's content.

Question to AskWhat It RevealsExample: A 1942 War Poster
Who created it and what was their position?Authority, perspective, potential bias.Created by a government agency (e.g., U.S. Office of War Information). It represents an official, pro-war perspective.
Who was the intended audience?Purpose and persuasive techniques used.The general public, especially civilians on the home front. Its purpose is to boost morale and encourage support for the war effort (like buying war bonds).
What is the main message and how is it conveyed?Meaning, use of symbols, emotion, and logic."United we win." It uses strong imagery of a white and a Black worker side-by-side, promoting unity and patriotism to achieve a common goal.
What is left out?Silences, limitations, and selectivity.It does not show the horrors of battle, racial tensions that still existed in the U.S., or the perspectives of conscientious objectors.

Case Study in the Classroom: The "Thanksgiving" Paintings

Let's apply these skills to a concrete example familiar to many students: common paintings of the "First Thanksgiving." These classic images often show Pilgrims and Native Americans sharing a peaceful, bountiful meal.

Step 1: Source Identification. The famous paintings by artists like Jean Leon Gerome Ferris (c. 1912-1915) are secondary sources. They were created nearly 300 years after the 1621 event in Plymouth[1]. They are interpretations, not eyewitness accounts.

Step 2: Analyzing Context and Purpose. Why were these paintings created in the early 1900s? This was a time of large-scale immigration to the United States. These images served a national purpose: to present a simplified, harmonious story of American origins, promoting unity and patriotism. The artists were not trying to be historically accurate archaeologists; they were myth-makers for their own time.

Step 3: Checking Against Primary Sources. To evaluate the painting's historical value, we turn to primary sources. Governor William Bradford's journal, Of Plymouth Plantation, and a letter by colonist Edward Winslow mention a harvest feast in 1621 attended by about 90 Wampanoag[2] men and 50 colonists. The primary accounts are brief and describe games and military exercises, not a solemn, seated dinner. They mention fowl and deer, but not the pies, roasted turkeys, and cornucopias shown in the paintings.

Step 4: Assessing Meaning and Value. The analysis reveals that the paintings are more valuable for understanding early 20th-century American ideals than 17th-century history. Their meaning is about unity and abundance as national values. Their reliability for facts about the 1621 event is low because they lack contemporary detail and reflect a later agenda. However, their value is high for a different historical question: "How did Americans in the 1900s view their founding myths?" This case perfectly shows how a source can be unreliable for one purpose but immensely valuable for another.

Important Questions

Q: If a primary source is from the time, does that automatically make it 100% true and reliable?

A: No. Being a primary source only means it is firsthand evidence from the period. It does not guarantee accuracy. The creator might have been misinformed, lying, exaggerating, or have forgotten details. A soldier's letter home might downplay dangers to not worry his family. A political speech will present only one side of an argument. Primary sources must still be cross-checked (corroborated) and analyzed for bias and purpose.

Q: How do you analyze a source that has no author, like an anonymous photograph or an ancient tool?

A: You focus even more on the other "Ws." For a photograph, ask: What does it show? (Content analysis). When and Where was it likely taken? (You can look at clothing, technology, architecture). Why might it have been taken? (Documentation, art, propaganda?). For a tool, scientists use techniques like carbon dating[3] to find "When," and they compare it to similar objects from known locations to guess "Where." The "What" and "How" (its design and wear marks) can tell you about its use and the people who made it.

Q: Is a history textbook a reliable source?

A: A textbook is a secondary source that summarizes and interprets many primary sources and other historical works. Its reliability comes from the fact that teams of scholars usually write and review it, and it should cite its evidence. However, it still has limitations: it simplifies complex events, it can reflect the biases of its time and place of publication, and it must select which stories to tell. The best approach is to use a textbook as a trusted starting point and map, but always remember that it is an interpretation, not the final word. Good historians look at the primary sources behind the textbook's claims.
Conclusion
Source analysis transforms history from a simple list of dates and names into an active, engaging process of inquiry. It empowers you to be a critical consumer of information, a skill vital not just for history class but for navigating news, social media, and everyday life. By learning to ask who, what, when, where, why, and how, you unlock the stories hidden within evidence. You learn that every source has a perspective, and truth is built by comparing multiple perspectives against the facts. Whether you're looking at a faded letter, a viral video, or a chapter in a book, the detective's toolkit of source analysis helps you separate fact from opinion, evidence from myth, and build a more accurate and thoughtful understanding of the world, past and present.

Footnote

[1] Plymouth: The location of the English colonial settlement established in 1620 in present-day Massachusetts, USA, associated with the Pilgrims and the Mayflower ship.
[2] Wampanoag: The name of the confederation of Native American tribes who lived in the region where the Plymouth Colony was established and who interacted with the Pilgrim settlers.
[3] Carbon Dating (Radiocarbon Dating): A scientific method used to determine the age of an object containing organic material by measuring the amount of radioactive carbon-14 ($^{14}C$) it contains.

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