Contextualizing Period 5, 1844-1877

By the end of this lesson, students will be able to:

• Explain why Period 5 is conventionally bounded by 1844 (Polk's election on a Manifest Destiny platform) and 1877 (the Compromise of 1877 and the end of Reconstruction).
• Identify the three major historical developments that organize Unit 5: westward expansion and migration, the deepening sectional crisis over slavery, and the Civil War with its contested reconstruction.
• Trace the causal arc that connects the annexation of Texas in 1845 to the Mexican-American War, the territorial disputes that followed, the failure of compromise in the 1850s, and the secession crisis of 1860 and 1861.
• Use Skill 4 (Contextualization) to situate at least one Period 5 development inside its broader continental, transatlantic, and constitutional setting.
• Account for the continuities that connect antebellum sectionalism to postwar Reconstruction politics, and the shifts that distinguish Period 5 from Period 6 (the era of industrialization and the New South).

Period 5 is the hinge of the AP US History course. In 1844, the United States was a continental republic that ended at the Louisiana Purchase line, that still tolerated slavery in fifteen states, and that had patched together every previous sectional crisis through compromise. By 1877, the country reached the Pacific, slavery had been abolished by constitutional amendment, the Confederacy had been defeated in the bloodiest war in American history, and the federal government had begun and abandoned the project of guaranteeing the civil and political rights of formerly enslaved Americans. Three braided developments produced that transformation: continental expansion, sectional crisis, and Civil War with Reconstruction (KC-5.1, KC-5.2, KC-5.3).

Continental expansion is the development that opens the period (KC-5.1). The doctrine of Manifest Destiny, named in an 1845 editorial by John L. O'Sullivan, fused popular enthusiasm for territorial growth with economic and security arguments to demand that the United States reach the Pacific (KC-5.1.I, KC-5.1.I.B). Polk's election in 1844 turned that demand into federal policy. Within four years, the Texas annexation of 1845, the Oregon Treaty of 1846 that fixed the northern border at the forty-ninth parallel, and victory in the Mexican-American War of 1846 to 1848 added more than 1.2 million square miles to the United States (KC-5.1.I.C). Migration filled in what diplomacy and conquest secured: hundreds of thousands of settlers walked the Oregon and California Trails, the discovery of gold at Sutter's Mill in 1848 set off the largest single-year migration in American history, and the Latter-day Saints reached the Great Basin in 1847 in a religious migration that would make Utah a distinctive western society. The lands the United States had absorbed were not empty; expansion brought the federal government into deepening conflict with Mexican Americans in the Southwest and with the Plains and Southwest American Indian nations whose territories the new boundary now bisected (KC-5.1.II.C). The same decades brought the largest wave of European immigration the country had yet seen, mostly Irish Catholics fleeing famine and German Catholics and Protestants fleeing political turmoil, and that influx provoked an organized anti-Catholic nativist reaction whose American Party (the Know-Nothings) briefly looked as though it might replace the Whigs as the second major party (KC-5.1.II.A, KC-5.1.II.B).

Continental expansion produced the sectional crisis that defines the middle of the period (KC-5.2). Every acre the United States gained from Mexico raised the same constitutional question: would the lands be slave or free? The Wilmot Proviso of 1846 proposed to ban slavery in any territory acquired from Mexico and was passed by the House but blocked in the Senate, exposing how cleanly the slavery question now mapped onto sectional lines. The Compromise of 1850 admitted California as a free state, organized Utah and New Mexico under popular sovereignty, and tightened the Fugitive Slave Act in a deal Henry Clay and Stephen Douglas brokered to hold the Union together for one more decade (KC-5.2.II.A, KC-5.2.II.B.i). The Kansas-Nebraska Act of 1854 then reopened the question by repealing the Missouri Compromise line and applying popular sovereignty to land that had already been declared free, igniting the violence of Bleeding Kansas (KC-5.2.II.B.ii). The Dred Scott decision of 1857 held that Black Americans were not citizens and that Congress had no power to ban slavery in the territories at all, a ruling that radicalized Northern opinion and convinced abolitionists that the federal judiciary itself had been captured by the slave power (KC-5.2.II.B.ii). The Lincoln-Douglas debates of 1858 sharpened the underlying disagreement on a free-labor versus slaveholding economy (KC-5.2.I.A, KC-5.2.I.B, KC-5.2.I.C); John Brown's raid on Harpers Ferry in 1859 convinced many white Southerners that the abolitionist movement was prepared to use force; and the Second Party System that had held the country together since the 1830s collapsed, replaced by an explicitly Northern Republican Party and a Southern-dominated Democratic Party that could no longer bridge the gap (KC-5.2.II.C). The Republican victory in the election of 1860 brought Abraham Lincoln to the presidency without a single Southern electoral vote, and within four months seven slave states had seceded and formed the Confederate States of America (KC-5.2.II.D).

The Civil War of 1861 to 1865 was the bloodiest conflict in American history (KC-5.3). It killed roughly 750,000 soldiers, more than every other American war combined through Vietnam, and it freed nearly four million enslaved people (KC-5.3.I.A). The Union began the war fighting only to preserve the federal compact, but Lincoln's Emancipation Proclamation of January 1, 1863, redefined the war as a struggle against slavery, prevented European powers from extending diplomatic recognition to the Confederacy, and opened the Union ranks to Black soldiers, roughly 180,000 of whom would serve before the war ended (KC-5.3.I.B). The Gettysburg Address that November distilled the redefined war into a single argument that the Union cause was the fulfillment of the founding promise that all men are created equal (KC-5.3.I.C). The Confederacy fought with skill and initiative, but the Union's larger population, deeper industrial base, more developed rail network, and Lincoln's eventual willingness to back generals such as Ulysses S. Grant and William T. Sherman who would wage total war produced victory at Vicksburg, Atlanta, and finally Appomattox (KC-5.3.I.D). The Thirteenth Amendment, ratified in December 1865, abolished slavery throughout the United States.

Reconstruction was the contested attempt to rebuild the defeated South and define what freedom would mean (KC-5.3.II.i). Presidential Reconstruction under Andrew Johnson restored white-only governments to most former Confederate states by late 1865, governments that immediately enacted Black Codes designed to bind freed people to plantation labor under conditions only marginally distinguishable from slavery (KC-5.3.II.C). Radical Republicans in Congress responded by seizing control of Reconstruction policy, dividing the South into five military districts, requiring new state constitutions that guaranteed Black male suffrage, and writing both the Fourteenth Amendment, which extended birthright citizenship and equal protection of the laws to all persons born or naturalized in the United States, and the Fifteenth Amendment, which barred racial discrimination in voting (KC-5.3.II.A). Roughly 2,000 Black men served in elected office during Reconstruction, sixteen in Congress and two in the Senate. The Freedmen's Bureau opened thousands of schools, and the integrated state legislatures of the Reconstruction-era South built the first universal public school systems any Southern state had ever known.

The end of the period is also the failure of the period (KC-5.3.II.C). White paramilitary groups such as the Ku Klux Klan, the White League, and the Red Shirts terrorized Black voters and Republican officeholders across the South. Northern public opinion gradually tired of military occupation, and a series of Supreme Court decisions narrowed the reach of the Reconstruction amendments. The disputed presidential election of 1876 between Rutherford B. Hayes and Samuel Tilden was settled in early 1877 by an informal bargain: Southern Democrats accepted the Republican Hayes as president, Hayes withdrew the last federal troops from the South, and the project of Reconstruction came to an end. The constitutional amendments survived; the political will to enforce them did not. By 1877, the South was returning to one-party Democratic rule, sharecropping was binding most freed people to land they did not own, and the era of legal segregation was beginning (KC-5.3.II.D, KC-5.3.II.E).

Several themes will recur across the next eleven lessons. The GEO theme tracks how expansion remade the continental and demographic map of the United States. The WOR theme follows imperial competition with Britain over Oregon, war with Mexico, and the diplomatic struggle between the Union and the Confederacy for European recognition. The NAT theme traces how Americans defined and contested the boundaries of citizenship and nationhood through compromise, secession, and the Reconstruction amendments. The PCE theme follows the realignment that produced the Republican Party, secession, and Radical Reconstruction. The ARC and SOC themes carry the comparison between free-labor and slaveholding economies and the social structures of the postwar South. Topics 5.1 and 5.12 are unit-synthesis lessons rather than thematic lessons; the CED page assigns them no single Thematic Focus, and the canonical map preserves that distinction.

A contextualizing lesson works best when it samples sources that span the period. The four excerpts below mark the ideological opening, the demographic midpoint, the constitutional break, and the curricular framework of Period 5.

1. (Continuity and Change) Compare the United States in 1844 with the United States in 1877. Identify two continuities and two significant shifts. Which set is more historically consequential, and on what grounds?
2. (Causation) Trace the causal chain that runs from the annexation of Texas in 1845 to the secession of South Carolina in December 1860. At which step in the chain do you think a different decision could have produced a different outcome, and why?
3. (Comparison) Compare the Compromise of 1850 with the Kansas-Nebraska Act of 1854. Both attempted to settle the question of slavery in newly organized territories; one bought the Union a decade and the other helped destroy it. What accounts for the different outcomes?
4. (Continuity and Change) The Reconstruction amendments rewrote the Constitution to extend citizenship, equal protection, and voting rights without regard to race. Identify one way the amendments transformed the legal order and one way the political order resisted that transformation between 1865 and 1877. Why did the amendments outlast the political project that produced them?
5. (Causation) Account for the global setting that shaped the Civil War. How did developments in Britain, France, and the Atlantic cotton economy between 1850 and 1865 shape what was possible inside the war the United States fought with itself?

Draft alignment — pending educator review. AP USH codes correspond to the official College Board Course and Exam Description (Effective Fall 2023, Version 1). Statements below are paraphrased in the CountryReports voice; refer to the College Board's published CED for verbatim wording.