AP U.S. History / Period 5: 1844–1877
Lesson
The Union breaks over slavery's future
Compromise failed as parties and regions polarized.
Learning goals
- Explain how expansion and party collapse led toward war.
- Distinguish a short-term trigger from a long-term cause.
Explanation
By the 1850s, national parties could no longer paper over slavery. New territories, a harsher fugitive-slave law, violence in Kansas, and a Supreme Court decision that denied Black citizenship all raised the stakes. Northern free-soil voters and Southern defenders of slavery stopped sharing a workable center.
Secession followed Lincoln's election, but the election was a trigger sitting on years of conflict. The war that followed was about whether a slaveholding republic could survive and whether the federal government could stop disunion. Keep slavery at the center; 'states' rights' is incomplete unless you say rights to do what.
Key terms
- secession. The attempt by slaveholding states to leave the Union after the 1860 election.
- free soil. The political position that slavery should not expand into new territories.
Common mistakes
- Explaining the Civil War as a sudden argument about tariffs or culture with slavery as a footnote.
- Collapsing 1848–1861 into a single event instead of a breakdown of institutions.
Practice
Original Marlow Works items. Check the answer explanation after you try.
Identify one way Reconstruction changed African American political participation in the South, and explain one limit on that change by the late 1870s.
Original Marlow Works item — not a College Board question.
Take your time—this is practice, not a test.
Answer explanation
What question makes 'states' rights' a usable historical phrase?
Answer. Rights to do what? In this crisis, the contested right was the protection and expansion of slavery.
Without the policy at stake, the phrase hides the cause.
Related resources
External links with reuse status. Marlow Works is independent and does not copy restricted exam or textbook material.
Official / link only
AP U.S. History course page
Official nine-period framework, skills, and exam updates.
College Board · All rights reserved · accessed 2026-10-01
Open sourceCC BY — attribution required
U.S. History (Open Textbook Library)
Open U.S. history textbook for chronology and institutions background.
Open Textbook Library listing · CC BY · accessed 2026-10-01
Open source