On October 29, 1929, prices on the New York Stock Exchange fell so sharply that the day became known as Black Tuesday. Many students write that the crash caused the Great Depression and stop there. It's a start, but it isn't an argument yet. Historians and economists point to several causes, including bank failures, weak farm incomes through the 1920s and falling demand, and they have long debated how much weight each one deserves. Deciding which cause mattered most, and showing how one led to another, is historical reasoning.
The three reasoning processes
The AP US History Course and Exam Description (CED) names three: comparison, causation, and continuity and change over time (CCOT). They sit inside Skill 5, Making Connections, and Skill 6.C asks you to use historical reasoning to explain how pieces of evidence relate. Every unit in the CED ends with a reasoning topic, such as 1.7 Causation in Period 1 or 2.8 Comparison in Period 2. On the exam, the multiple-choice questions, the DBQ, the LEQ, and at least one short-answer question all assess this skill.
The CED breaks each process into tasks. Each list starts with describe (say what the causes, similarities or changes were), moves on to explain (say how or why), and ends with explaining relative significance (which one mattered most, and why).
Causation
Causation asks what led to a development and what it led to. The CED's five tasks run from describing causes and effects (2.i) to weighing them (2.v). Two distinctions matter most:
- Primary vs secondary causes. Not every cause carries equal weight. Say which one did the most work.
- Short-term vs long-term effects. The stock market crash had immediate effects on investors, while New Deal programs that responded to the Depression, such as Social Security in 1935, lasted for decades.
Task 2.iv links causation to context: explain how a broader situation shaped a development.
Comparison
Comparison asks how two developments were alike or different, and why. Compare the same aspect of each. The CED describes the Chesapeake colonies growing prosperous on tobacco, worked first by mostly male indentured servants and later by enslaved Africans, while New England developed small towns, family farms and a mixed economy of agriculture and commerce. Comparing their labor systems works; comparing Chesapeake crops with New England towns doesn't. Then explain the difference: tobacco was labor-intensive.
Continuity and change over time
CCOT asks what changed across a period and what stayed the same. Women's suffrage is a clear case. Delegates at the Seneca Falls Convention in 1848 called for the vote, and the Nineteenth Amendment, ratified in 1920, barred the United States and the states from denying citizens the vote on account of sex. That is change. But many Black women in the South were still kept from voting by the same poll taxes, literacy tests and intimidation used against Black men. That is continuity. The best answers say which mattered more for a particular group.
Matching the reasoning to the prompt
Prompts usually signal the process. "Relative importance of causes" means causation. "To what extent did ... change" means CCOT. "Similarities and differences" means comparison. In the LEQ, one point goes to using historical reasoning to frame or structure your argument, and the scoring notes say simply asserting it isn't enough. In both the LEQ and DBQ, explaining both sides of a process, such as both continuity and change, is one route the scoring guidelines list toward the complexity point.
Common mistakes students make
- Listing causes without linking them. "The market crashed and banks failed" is a list. Add because or which led to.
- Treating every cause as equal. Rank them.
- Comparing different aspects. Line up the same feature of each development.
- Writing only about change. "To what extent" asks about continuity too.
- Naming the process instead of using it. Saying "this shows causation" earns nothing if the argument isn't built on it.
Frequently asked questions
What are the APUSH historical thinking skills?
The CED lists six skills: developments and processes, sourcing and situation, claims and evidence in sources, contextualization, making connections, and argumentation. Making connections is where comparison, causation, and continuity and change come in.
What are the three historical reasoning processes in APUSH?
Comparison, causation, and continuity and change over time.
How do you write a CCOT essay in APUSH?
Make a claim about what changed and what stayed the same, support each with specific evidence, and explain which was more significant for the topic in the prompt.
What does CCOT mean in APUSH?
Continuity and change over time: explaining what changed across a period, what stayed the same, and which mattered more.
Try it
Pick the Great Depression. Write one sentence that names a primary cause and one that names a secondary cause, then explain why the first mattered more. What changed, and why then?
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