Summary
Highlights
In 1819, the United States was equally divided with 11 free and 11 slave states. The desire for westward expansion, driven by 'Manifest Destiny,' led to complications when Missouri and Maine sought statehood. Northern and Southern factions clashed over Missouri's potential as a slave state. Henry Clay's Missouri Compromise in 1820 allowed Missouri to enter as a slave state and Maine as a free state, while also establishing the 36º 30’ latitude line as the boundary for future free states in the Louisiana Purchase territory.
The Missouri Compromise led to a tit-for-tat entry of states (Arkansas, Michigan, Florida). Texas's request for annexation in 1845 as a slave state upset the balance. President James K. Polk, a proponent of Manifest Destiny, attempted to purchase territories from Mexico, but upon rejection, provoked the Mexican-American War. The Treaty of Guadalupe Hidalgo ceded vast territories to the U.S., reigniting debates over slavery in new lands.
The acquisition of new territories from Mexico, including California, led to the Compromise of 1850. California entered as a free state, but the decision of slavery in other new territories would be determined by popular sovereignty. This policy, applied to the Kansas-Nebraska Act in 1854, repealed the Missouri Compromise line and sparked 'Bleeding Kansas,' a period of violent conflict between pro-slavery and anti-slavery settlers.
The fundamental divide between North and South stemmed from vastly different cultural and economic systems. The industrialized North, less reliant on manual labor, began questioning the morality of slavery and leaned towards abolition. The agrarian South, economically dependent on slave labor for plantations, viewed any threat to slavery as an existential threat to their way of life. While federal vs. state rights played a role, the institution of slavery was the primary driver of tension.
Events further inflamed tensions, including the Fugitive Slave Act of 1850, which mandated federal assistance in returning escaped slaves and angered Northerners. This led to the formation of the Republican Party, an anti-slavery political entity that gained prominence with figures like Abraham Lincoln. 'Bleeding Kansas' saw intense guerrilla warfare as pro-slavery and anti-slavery factions fought for control, resulting in violence and a split government.
Senator Charles Sumner's impassioned anti-slavery speech led to a brutal assault by Southern congressmen, highlighting the extreme animosity. The 1857 Dred Scott v. Sandford Supreme Court case further escalated tensions. The ruling denied Dred Scott, a slave, his freedom and declared that African Americans could not be U.S. citizens, enraging abolitionists. In 1859, radical abolitionist John Brown led a failed raid on Harper's Ferry to spark a slave rebellion, ultimately being captured and executed, but becoming a martyr for the anti-slavery cause.
The election of Abraham Lincoln, an anti-slavery Northerner, as president in 1860 was the final trigger for Southern states. South Carolina seceded, followed by ten other Southern states, forming the Confederate States of America. Lincoln refused to acknowledge their legitimacy, aiming to preserve the Union. The Confederacy faced significant disadvantages in population, industrial capacity, and infrastructure compared to the Union. Tensions culminated with the Confederate attack on Fort Sumter in April 1861, marking the beginning of the Civil War.