ACT Reading — compare and cause: history and economics

Key Ideas and Details is the largest reporting category of the ACT Reading section; ACT describes it as roughly half the questions. Much of it is about relationships the writer sets up between ideas: what caused what, in what order, and how two cases compare. Social science and history passages are built on exactly these relationships, and the wrong answer choices are built on breaking them, most often by reversing a cause and its effect or by comparing two cases at different points.

This material gives you three original excerpts. A history article explains how the Erie Canal, opened in 1825 along the Mohawk River valley, cut the cost of shipping between the Great Lakes and New York City and why Pennsylvania, facing the Allegheny Mountains, could not match it. An economics piece follows two towns that each lost a factory and chose different responses, a tax break for a warehouse and a retraining program, and compares where they stood years later. An economics column traces how one late frost in a cherry-growing region changed prices, and then buyers' habits, for longer than the frost itself lasted.

Ten questions follow. You identify the cause the writer actually names, as opposed to a detail that merely accompanies it. You put a causal chain in the writer's order and spot choices that turn an effect into a cause. You compare two cases at matching points in time, explain why a writer contrasts one state's route with another's, and recognize a writer's caution that two towns with different surroundings are not an experiment. And you reject a conclusion, marked by words such as "always" and "any," that goes further than the evidence can.

Explanations quote the sentence that settles each answer and name the kind of error in each wrong choice. The flashcards list the signal words of cause and effect, the habit of ordering events by time before choosing, and the supply-and-demand reasoning that economics excerpts expect you to follow from the text itself.

The material offers a quiz and a flashcard deck. The Erie Canal excerpt keeps to well-established facts; the two economics excerpts describe invented towns and markets for practice. The material is written for students preparing for the ACT and is not produced or endorsed by ACT.

  • Identify the cause a writer names for an event or outcome
  • Order the links of a causal chain and reject reversed causes
  • Compare two cases at matching points
  • Recognize a writer's caution about comparing cases
  • Reject conclusions that generalize beyond the evidence

Practice material written by Zestly, based on ACT's published description of the ACT Reading section (reporting categories Key Ideas and Details, Craft and Structure, Integration of Knowledge and Ideas; act.org, retrieved September 2026). All passages are original.

Sample question

Read the following excerpt from a history article. In the early 1800s, the Appalachian Mountains stood between the farms of the Great Lakes region and the cities of the Atlantic coast. Hauling a wagonload of grain over the mountains often cost more than the grain was worth, so most western farmers grew little beyond what they and their neighbors could use. New York had one advantage no other seaboard state shared: the Mohawk River valley, a break in the mountains that ran west from the Hudson River almost to Lake Erie. The Erie Canal, opened in 1825, followed that valley from Albany to Buffalo. Because the route was nearly level, boats pulled by mules and horses could carry heavy loads cheaply, and the cost of shipping goods between the Great Lakes and New York City fell to a small fraction of what it had been. Western farmers could now sell to eastern markets, and their grain flowed east through New York's harbor while manufactured goods flowed west. Pennsylvania answered with its own system of canals and railways, but its route had to climb over the Allegheny Mountains, and it never carried goods as cheaply. Within a generation, New York City's lead over Philadelphia, Baltimore and Boston as a port had grown wider than ever. According to the writer, what made the Erie Canal's route possible where other routes were not?

See the answer

The Mohawk River valley offered a nearly level break in the mountains running west from the Hudson River.

The writer says New York had "one advantage no other seaboard state shared: the Mohawk River valley, a break in the mountains," and that the route "was nearly level." Mules and horses are how boats were pulled, not the reason for the route; Pennsylvania's system came afterward and never matched the canal's costs; and western farmers grew little surplus until the canal opened a market.

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