5.1 Contextualizing Period 5

Setting the Stage: Expansion Fuels Tension

By the 1840s, westward expansion and belief in Manifest Destiny pushed the U.S. toward the Pacific, adding vast new territories through the Mexican-American War (1846–1848) and Oregon settlement. This rapid growth reignited the explosive question of whether slavery would spread into new territories, deepening the sectional divide between North and South that had been simmering since the Missouri Compromise.

Sectionalism Intensifies

Economic differences hardened political divisions: the North industrialized with free labor and growing cities, while the South relied on cotton and enslaved labor. Compromises like the Compromise of 1850 and Kansas-Nebraska Act (1854) failed to resolve conflict, instead accelerating polarization, the rise of the Republican Party, and violence like 'Bleeding Kansas,' setting the stage for secession and the Civil War.

War, Reconstruction, and Lasting Change

The Civil War (1861–1865) ended slavery via the 13th Amendment and preserved the Union, while Reconstruction (1865–1877) attempted to rebuild the South and define citizenship and rights for freedpeople through the 14th and 15th Amendments. Yet resistance, violence, and the Compromise of 1877 ultimately curtailed these gains, leaving a legacy of unresolved racial inequality.

Key terms

Manifest Destiny

The belief that the U.S. was destined to expand across North America, driving westward settlement and territorial acquisition.

Mexican-American War

1846–1848 conflict that resulted in the U.S. gaining vast southwestern territories, intensifying slavery expansion debates.

Sectionalism

Growing loyalty to regional (North vs. South) interests over national unity, fueled by economic and slavery-related differences.

13th Amendment

1865 constitutional amendment that abolished slavery throughout the United States.

Compromise of 1877

Political deal that resolved the disputed 1876 election by removing federal troops from the South, ending Reconstruction.

Try an AP-style question

Period 5 (1844–1877) is best characterized by…

1. colonial settlement and trade
2. the Great Depression
3. industrial monopolies
4. expansion, civil war, and Reconstruction