U.S. Westward Expansion & Sectional Tensions: Key Concepts and Events

U.S. Westward Expansion & Sectional Tensions: Key Concepts and Events

Manifest Destiny

The belief that the U.S. was destined to expand westward across North America. Drove westward settlement, helped cause the Mexican-American War, and increased sectional conflict over slavery in new territories.

Railroads

Expanding transportation networks that connected regions of the U.S. in the mid-1800s. Boosted national trade, opened the West to settlement, and increased federal land grant involvement; also shifted political and economic power.

Panic of 1857

A financial crisis caused by declining demand and overproduction, affecting the North most severely. Strengthened Southern belief in the superiority of the slave-based economy and widened sectional divisions before the Civil War.

Mountain Men

Fur trappers and explorers who lived in the Rocky Mountains and western frontier. Mapped trails and encouraged later migration west through their routes and reports.

Mining Frontier

Western areas rapidly settled after gold, silver, or other minerals were discovered. Led to boomtowns, population growth, Native displacement, and helped new states enter the Union.

Gold Rush

Mass migration to California after gold was discovered in 1848. Caused rapid population growth and helped push California into the Union as a free state.

Silver Rush

Major silver discoveries—especially in Nevada—that attracted miners. Stimulated western settlement and contributed to rapid territorial development.

Farming Frontier

Western lands settled by families seeking cheap, fertile farmland. Expanded agricultural production and permanently populated regions beyond the Mississippi River.

Urban Frontier

Fast-growing western towns and cities that developed alongside mining, farming, and trade. Created new economic centers and connected the West to national markets.

Federal Land Grants

Government land given to railroad companies to encourage construction. Enabled rapid railroad expansion and increased settlement while also leading to corruption scandals.

John Tyler

Tenth U.S. president who took office after William Henry Harrison’s death. Pushed for Texas annexation and often clashed with Whigs, weakening the party.

Oregon Territory

Large region in the Pacific Northwest claimed by both the U.S. and Britain. Became a major expansion goal; settlement increased demands for U.S. control, contributing to negotiations with Britain.

“Fifty-Four Forty or Fight!”

Polk’s expansionist slogan demanding U.S. control of Oregon up to latitude 54°40′. Reflected strong Manifest Destiny sentiment and pressured Britain to settle the Oregon boundary peacefully.

James K. Polk

Eleventh U.S. president known for aggressive expansionist goals. Oversaw the Mexican-American War, acquired California and the Southwest, and settled the Oregon boundary.

Wilmot Proviso

Proposal to ban slavery in any territory gained from Mexico. Passed in the House but not the Senate; heightened sectional tensions by making slavery expansion a national political issue.

Texas

Region settled by Americans under Mexican rule that later declared independence. Its annexation by the U.S. in 1845 helped trigger the Mexican-American War and intensified sectional conflict over slavery.

Stephen F. Austin

Leader who brought the first major group of American settlers into Mexican Texas. His colony’s success increased U.S. migration into Texas, eventually contributing to tensions with Mexico and the push for independence.

Antonio López de Santa Anna

Mexican president and military leader during the Texas Revolution. His strict policies and attacks on Texan forces led to rebellion; his defeat at San Jacinto forced Mexico to recognize Texas independence.

Sam Houston

Commander of Texan forces and first president of the Republic of Texas. Led Texas to victory at San Jacinto and pushed for U.S. annexation, shaping the road toward the Mexican-American War.

Alamo

1836 battle in which Mexican forces defeated Texan defenders at a mission in San Antonio. Became a symbol of Texan resistance and fueled support for independence.

Webster-Ashburton Treaty (1842)

Agreement between the U.S. and Britain settling the Maine–Canada border. Reduced U.S.–British tensions and secured territory for both nations.

Foreign Commerce

Expansion of U.S. trade with global markets in the mid-1800s. Strengthened the U.S. economy and supported Manifest Destiny by encouraging Pacific and Asian trade.

Exports and Imports

Goods sold abroad (exports) and goods brought in (imports). Growing international trade helped fuel industrialization and western port expansion.

Matthew C. Perry

U.S. naval officer sent to Japan in the 1850s. Forced Japan to open trade with the U.S., increasing American influence in Asia.

Kanagawa Treaty (1854)

Treaty between the U.S. and Japan opening Japanese ports to American ships. Ended Japan’s isolation and strengthened U.S. access to Asian markets.

Mexican-American War (1846–1848)

Conflict between the U.S. and Mexico triggered by territorial disputes after Texas annexation. Resulted in major U.S. land gains (the Mexican Cession) and intensified national debates over slavery in new territories.

California

Western territory claimed by the U.S. during the Mexican-American War. Became a key part of the Mexican Cession and quickly grew due to the Gold Rush.

Rio Grande

River claimed by the U.S. as the southern border of Texas. Dispute over this boundary helped spark the Mexican-American War.

Zachary Taylor

U.S. general whose forces fought in northern Mexico; later became president. His victories built support for the war and increased his national political popularity.

Bear Flag Republic

Short-lived independent republic declared by American settlers in California in 1846. Helped justify U.S. takeover of California during the Mexican-American War.

Mexican Cession

Large territory (California, Nevada, Utah, and parts of others) Mexico ceded to the U.S. in 1848. Expanded the U.S. dramatically and led to fierce debates over whether slavery would expand west.

Treaty of Guadalupe Hidalgo

Treaty that ended the Mexican-American War. Recognized U.S. control of Texas, set the Rio Grande as the border, and gave the U.S. the Mexican Cession.

Ostend Manifesto (1854)

Secret U.S. diplomatic message proposing to buy Cuba from Spain and take it by force if necessary. Angered Northern abolitionists, who saw it as an attempt to expand slavery.

Walker Expedition

Private military invasions of Central America led by William Walker. Tried to seize Nicaragua to expand slavery; condemned internationally and embarrassed the U.S.

Gadsden Purchase

Land bought from Mexico in 1853 (southern Arizona/New Mexico). Helped complete a southern transcontinental railroad route.

Free-Soil Movement

Northern movement opposing expansion of slavery into western territories. Laid the foundation for the Republican Party.

Free-Soil Party

Political party (1848) opposing the extension of slavery. Shifted national politics by making slavery expansion a major issue.

Henry Clay

Senator known as the “Great Compromiser.” Authored major compromises, including the Compromise of 1850, to reduce sectional conflict.

Compromise of 1850

Package of laws settling disputes after the Mexican Cession. Admitted California as free, strengthened the Fugitive Slave Law, and temporarily eased sectional tensions.

Popular Sovereignty

Idea that settlers in a territory should vote on slavery. Became central to the Kansas-Nebraska Act and triggered violence in Kansas.

Nativism

Anti-immigrant movement, especially against Irish and German Catholics. Led to the rise of the Know-Nothing Party.

Tammany Hall

Democratic political machine in New York City. Gained power through immigrant votes and became known for corruption.

Fugitive Slave Law (1850)

Law requiring citizens to help return escaped enslaved people. Outraged Northerners and increased abolitionist resistance.

Underground Railroad

Secret network helping enslaved people escape to freedom. Freed thousands and angered Southern slaveowners.

Harriet Tubman

Former enslaved woman and key conductor on the Underground Railroad. Helped hundreds escape slavery and became a symbol of abolition.

Uncle Tom’s Cabin

Antislavery novel by Harriet Beecher Stowe. Inspired Northern opposition to slavery and infuriated the South.

Harriet Beecher Stowe

Author of Uncle Tom’s Cabin. Her book shifted public opinion and strengthened the abolition movement.

Bleeding Kansas

Violent clashes between proslavery and antislavery settlers in Kansas. Previewed the Civil War and showed the failure of popular sovereignty.

Pottawatomie Creek

John Brown’s raid in Kansas where he killed proslavery settlers. Escalated sectional violence.

Lecompton Constitution

Proslavery constitution proposed for Kansas. Rejected after national controversy; showed the deep divide within the Democratic Party.

Stephen A. Douglas

Illinois senator and proponent of popular sovereignty. Authored the Kansas-Nebraska Act and debated Lincoln in 1858.

Kansas-Nebraska Act (1854)

Law allowing popular sovereignty in Kansas and Nebraska. Repealed the Missouri Compromise, caused violence, and led to the Republican Party’s creation.

Know-Nothing Party

Anti-immigrant, anti-Catholic political party. Gained influence in the 1850s but collapsed over sectional divisions.

Republican Party

New political party formed in 1854 to oppose slavery expansion. Quickly became the major Northern party and elected Abraham Lincoln in 1860.

John C. Fremont

First Republican presidential candidate in 1856. Represented the anti-slavery platform and strengthened the Republican Party in the North.

Millard Fillmore

13th U.S. president, successor to Zachary Taylor. Supported the Compromise of 1850, including the Fugitive Slave Law, trying to ease sectional tensions.

James Buchanan

15th U.S. president, in office before the Civil War. Failed to stop Southern secession and is widely criticized for weak leadership during the sectional crisis.

Dred Scott v. Sanford (1857)

Supreme Court case ruling that African Americans were not citizens and Congress could not ban slavery in territories. Heightened sectional tensions and invalidated the Missouri Compromise.

Roger Taney

Chief Justice of the Supreme Court who decided Dred Scott. His ruling fueled Northern anger and strengthened the Republican anti-slavery movement.

Lincoln-Douglas Debates (1858)

Series of debates between Abraham Lincoln and Stephen Douglas during the Illinois Senate race. Highlighted national divisions over slavery and raised Lincoln’s profile for the 1860 election.

Abraham Lincoln

16th U.S. president, elected in 1860 as a Republican. Led the Union through the Civil War and issued the Emancipation Proclamation.

Freeport Doctrine

Stephen Douglas’ argument that territories could effectively exclude slavery despite the Dred Scott decision. Split the Democratic Party and fueled sectional conflict before the 1860 election.

Sumner-Brooks Incident (1856)

Congressman Preston Brooks attacked Senator Charles Sumner with a cane on the Senate floor. Symbolized the violent tensions between North and South over slavery.

John Brown

Radical abolitionist who led violent raids against proslavery forces. His actions at Pottawatomie and Harpers Ferry increased sectional tensions.

Harpers Ferry (1859)

John Brown’s raid on a federal arsenal in Virginia. Intended to start a slave revolt; it failed but alarmed the South and pushed the nation closer to war.

Secession

Formal withdrawal of Southern states from the Union. Triggered the Civil War after Lincoln’s election in 1860.

Border States

Slave states that did not secede (e.g., Kentucky, Maryland, Missouri, Delaware). Critical to Union strategy for resources, geography, and political support.

Fort Sumter

Federal fort in Charleston Harbor, South Carolina. Confederate attack in April 1861 marked the start of the Civil War.

Jefferson Davis

President of the Confederate States of America. Led the Confederacy during the Civil War, overseeing its political and military strategies.

Confederate States of America

Government formed by 11 Southern states that seceded. Its creation formalized the divide leading to the Civil War.

Bull Run (First, 1861)

First major battle of the Civil War in Virginia. Showed the war would be longer and bloodier than expected.

Winfield Scott

Union general who developed the Anaconda Plan. Designed a strategy to blockade and divide the Confederacy, aiming for a long-term Union victory.

Anaconda Plan

Union strategy to blockade Southern ports and control the Mississippi River. Successfully weakened Confederate resources and split their territory.

George B. McClellan

Union general known for cautious tactics. Often delayed attacks, frustrating Lincoln and slowing early Union progress.

Robert E. Lee

Confederate general and military leader. Won major battles for the Confederacy but eventually surrendered at Appomattox.

Antietam (1862)

Bloodiest single-day battle in American history. Gave Lincoln the opportunity to issue the Emancipation Proclamation.

Fredericksburg (1862)

Major Confederate victory in Virginia. Demonstrated Union struggles and boosted Confederate morale.

Ulysses S. Grant

Union general and later president. Led Union forces to victory in the West and eventually overall command in 1864.

Vicksburg (1863)

Key Confederate stronghold on the Mississippi River. Its capture gave the Union full control of the Mississippi, splitting the Confederacy.

Gettysburg (1863)

Major Civil War battle in Pennsylvania. Turning point in the war; ended Lee’s invasion of the North and boosted Union morale.

Sherman’s March / William Tecumseh Sherman

Union general’s destructive campaign through Georgia and the South. Devastated Southern infrastructure, weakened Confederate morale, and helped bring the war to an end.

Appomattox Court House (1865)

Site in Virginia where Lee surrendered to Grant. Marked the end of the Civil War.

Greenbacks

Paper currency issued by the Union during the Civil War. Helped finance the war but caused inflation.

Morrill Tariff Act (1861)

Increased tariffs on imported goods. Protected Northern industries and raised revenue for the Union.

Morrill Land Grant Act (1862)

Granted land to states to fund agricultural colleges. Encouraged higher education in agriculture and engineering.

Pacific Railway Act (1862)

Law providing federal support for building a transcontinental railroad. Linked the country economically and facilitated western settlement.

Homestead Act (1862)

Granted 160 acres of western land to settlers who improved it. Encouraged westward migration and expansion of farming.

Habeas Corpus

Legal protection against unlawful imprisonment. Lincoln suspended it during the Civil War to maintain order, causing controversy over civil liberties.

Confiscation Acts

Laws allowing Union forces to seize Confederate property, including enslaved people. Weakened the Confederacy and paved the way for emancipation.

Emancipation Proclamation (1863)

Executive order freeing enslaved people in Confederate states. Shifted the war focus to ending slavery and prevented European support for the Confederacy.

Copperheads

Northern Democrats opposing the Civil War. Created political opposition to Lincoln and challenged Union war policies.

Gettysburg Address (1863)

Lincoln’s speech dedicating a cemetery at Gettysburg. Reframed the war as a fight for freedom and equality.

Massachusetts 54th Regiment

First major African American regiment in the Union army. Proved African Americans’ courage and helped promote black enlistment.

13th Amendment (1865)

Constitutional amendment abolishing slavery. Legally ended slavery in the United States.

Civil Rights Act of 1866

Law granting citizenship and equal rights to African Americans. Countered Black Codes and laid groundwork for Reconstruction amendments.

14th Amendment (1868)

Constitutional amendment granting citizenship and equal protection under the law. Strengthened civil rights and limited state power over individuals.

Equal Protection Laws

Legal principles ensuring all citizens are treated equally by the law. Basis for civil rights protections after the Civil War.

Due Process of Law

Constitutional guarantee of fair legal procedures. Protected individuals from arbitrary state actions, central to the 14th Amendment.

15th Amendment (1870)

Constitutional amendment granting African American men the right to vote. Extended political rights and reshaped Southern politics during Reconstruction.

Civil Rights Act of 1875

Law guaranteeing African Americans equal treatment in public accommodations. Largely unenforced but represented federal attempts to protect black rights.