Causes of the Civil War

In April 1861 the Civil War began. Seven Southern states had already left the United States and formed a new government, the Confederate States of America. Historians have studied the causes for generations, and the textbook consensus is clear: the central cause was slavery, and above all the disagreement over whether slavery would spread into the new western territories. Other factors mattered too, including tariffs, the balance of political power and competing views of federal power. This lesson separates four things that are easy to mix up: the central cause, other factors, the events that raised tension, and the triggers that began the war. It also listens to people who lived through the crisis, including enslaved and free Black Americans and abolitionists. It covers causes only. The battles and the years after the war are separate lessons.

Central cause, other factors, events and triggers

Historians sort the reasons for a war into different kinds, and the sorting matters. This lesson uses four labels.

• Central cause: the deepest and most important reason. For the Civil War, the textbook consensus is that this was slavery, and above all the disagreement over whether slavery would spread into the western territories.
• Other factors: real issues that added to the conflict, such as tariffs (taxes on imported goods), the balance of political power between North and South, and competing views of how much power the federal government should have.
• Events: the laws, court rulings, books and acts of violence between 1820 and 1859 that made the disagreement sharper.
• Triggers: the events that set off the final break: the election of Abraham Lincoln in November 1860, the secession of Southern states, and the attack on Fort Sumter in April 1861.

A cause-and-effect map is a simplified picture. Real events had many contributing factors, and real people made choices at every step. Nothing on the map happened automatically.

Two societies: the North and the South

By the early 1800s every Northern state had either ended slavery or passed a law to end it gradually. The Northern economy grew through industry: factories, railroads, banking and trade. Northern cities grew fast. Millions of immigrants, many of them from Ireland and Germany, arrived in the 1840s and 1850s and settled mostly in the North and Midwest. Most work was done by free labor: wage workers in factories and families farming their own land.

The South's economy was built on plantation agriculture. Large farms grew cotton, tobacco, rice and sugar for sale, and they depended on the forced labor of enslaved people. After the invention of the cotton gin in the 1790s made it easier to process cotton, cotton farming spread west across the South and the demand for enslaved labor grew. By 1860 nearly four million people were enslaved in the United States. In the law of the slave states, enslaved people were property. They could be bought and sold, and families could be torn apart by sale. Enslaved people received no pay, had no freedom to leave, and had almost no legal protection from the people who held them. Slaveholders used violence, including whipping, to force people to work and to punish resistance. Most white Southern families did not enslave anyone, but slaveholders held much of the region's wealth and political power. Compared with the North, the South had fewer cities, fewer factories and fewer immigrants.

The two sections were not separate worlds. Northern textile mills used Southern cotton, and Northern banks and shippers made money from the cotton trade. The North was also not free of racism: free Black Northerners faced discrimination, and many white Northerners who opposed slavery's spread did not support equal rights. A different economy does not by itself cause a war. The difference that mattered was that one section's economy rested on slavery and the other's did not, in a country that had to decide whether slavery would grow.

Why the western territories mattered

Each time the United States added land in the West, Congress and the settlers had to answer a question: would slavery be allowed there? A free state was a state where slavery was banned, and a slave state was one where it was legal. A territory was land the United States owned that had not yet become a state. Whether a territory would become free or slave was the heart of the dispute, for three reasons.

First, power. Every new state sent two senators and some representatives to Congress. For years Congress tried to keep the number of free and slave states equal in the Senate, so that neither side could outvote the other on laws about slavery.

Second, the future of slavery. Many Southern leaders feared that if slavery could not spread, the free states would keep growing stronger and might one day limit or end slavery.

Third, morals and opportunity. Abolitionists believed slavery was a great wrong done to enslaved people. Many other Northerners opposed slavery's spread for mixed reasons: some thought it was wrong, and some wanted western land reserved for free white farmers and workers. Because these motives were mixed, Northern opinion was divided.

Compromises that did not settle the question

The Missouri Compromise (1820). Missouri asked to join the Union as a slave state. Many Northern members of Congress objected, partly because it would tip the balance in the Senate. Congress settled the matter with a package of laws. Maine would enter as a free state and Missouri as a slave state, and slavery would be banned in the rest of the Louisiana Purchase north of the line at 36°30′ north latitude. South of the line, slavery stayed legal. The line stayed in place for more than thirty years, but it settled the question only for that one stretch of land.

The Compromise of 1850. The war with Mexico (1846 to 1848) added a huge area in the Southwest and on the Pacific coast, including California. The question came back at once: would slavery spread into this land? In 1850 Congress passed a package of laws called the Compromise of 1850. Among other things, California entered the Union as a free state. Settlers in the New Mexico and Utah territories would decide the question of slavery for themselves. Buying and selling enslaved people (the slave trade, not slavery itself) was banned in Washington, D.C. And a much stronger Fugitive Slave Act was passed, as a concession to the South.

The Fugitive Slave Act. This federal law said that people who had escaped slavery must be returned to the people who claimed them, even if they were caught in a free state. Officials and ordinary citizens could be required to help. A person accused of being an escapee had no right to a jury trial and could not testify in his or her own defense. Free Black people in the North could be accused too. Many Northerners were angry at being made part of slavery. Some Northern states passed laws that limited their own officials' role in returning people. Some Black families in the North, afraid of being seized, moved to Canada.

Voices against slavery: resistance, abolitionists and the Underground Railroad

Slavery was never just a debate among white politicians. Enslaved people resisted in many ways, from slowing down work and learning to read in secret to running away. Free Black Americans in the North built churches, newspapers and organizations and spoke out against slavery.

An abolitionist is a person who worked to end slavery. The movement included Black and white people, women and men. William Lloyd Garrison, a white abolitionist in Boston, began publishing the newspaper The Liberator in 1831 and demanded that slavery end immediately. Frederick Douglass was born into slavery in Maryland and escaped in 1838. He became one of the most powerful speakers and writers of his time. He published the story of his life in 1845, and in 1847 he started his own newspaper, the North Star. Harriet Tubman escaped from slavery in Maryland in 1849. She later went back to the South several times to guide family members and others to freedom.

The Underground Railroad was not a real railroad. It was a secret network of Black and white people, routes and safe houses that helped enslaved people escape to the free states and to Canada. It borrowed words from railroads, such as “station” and “conductor.” Each escape was an act of courage and a risk. People who were caught could be returned to slavery, and people who helped them could be punished. Together, escapes, speeches, newspapers and books made it harder for the country to ignore slavery.

Not all Northerners were abolitionists. Many opposed slavery's spread without calling for its end where it already existed, and abolitionists were often unpopular, even in the North.

How a novel moved opinion: Uncle Tom's Cabin (1852)

In 1852 Harriet Beecher Stowe published the novel Uncle Tom's Cabin. She wrote it partly in anger at the Fugitive Slave Act. The story follows enslaved characters and shows families separated by sale and the cruelty of slavery. It was one of the most widely read books of its time. Many Northern readers, who had thought little about slavery, were moved to oppose it. Many white Southerners rejected the book as unfair and untrue.

Today historians add two cautions. The novel relies on stereotypes of Black people, and a novel is a persuasive work of fiction, not a record of events. It is still a good example of how the slavery question moved public opinion in the 1850s.

Kansas–Nebraska Act and Bleeding Kansas (1854 to 1859)

In 1854 Senator Stephen A. Douglas of Illinois led Congress to pass the Kansas–Nebraska Act. It created two new territories, Kansas and Nebraska, and said that popular sovereignty would decide the question of slavery there: the settlers would vote. Kansas and Nebraska lay north of the line at 36°30′, so the act also repealed the Missouri Compromise ban on slavery in that land. Many Northerners were angry that a ban they had relied on for more than thirty years was erased. The act helped break apart the Whig Party and led to the founding of a new party, the Republican Party, in 1854, to oppose the spread of slavery into the territories.

Kansas became a battleground. Pro-slavery and anti-slavery settlers rushed in to win the vote, and each side set up its own government. Fighting broke out, and the violence became known as “Bleeding Kansas.” In May 1856 pro-slavery men attacked the free-state town of Lawrence. Days later, John Brown and a group of followers killed five pro-slavery settlers near Pottawatomie Creek. In the same month, in Washington, a South Carolina congressman, Preston Brooks, beat Senator Charles Sumner of Massachusetts with a cane on the Senate floor, after Sumner gave a speech attacking pro-slavery forces in Kansas. The fighting in Kansas went on for several years, and Kansas entered the Union as a free state in January 1861.

The Dred Scott decision (1857)

Dred Scott was an enslaved man whose enslaver had taken him to live in Illinois, a free state, and in a territory where slavery was banned. Scott sued for his freedom, arguing that living on free soil had made him free. In March 1857 the Supreme Court ruled against him in Dred Scott v. Sandford. Chief Justice Roger B. Taney wrote the main opinion for a 7–2 majority. The Court held that Black Americans, whether enslaved or free, could not be citizens of the United States and so could not sue in federal court. It also held that Congress had no power to ban slavery in the territories, which meant the Missouri Compromise ban had been unconstitutional.

Slaveholders welcomed the ruling. Many Northerners, and the new Republican Party, were furious: the decision seemed to open every territory to slavery, and it denied citizenship to Black Americans, including those who were free. It also made compromise harder, because the Court had taken the question of slavery in the territories out of Congress's hands. (The Fourteenth Amendment, ratified in 1868, later overturned the Court's citizenship ruling. That belongs to the Reconstruction lesson.)

John Brown's raid (1859)

John Brown was a white abolitionist who believed that slavery could be ended only by force. In October 1859 he led a small group of followers, both white and Black, in a raid on the federal arsenal at Harpers Ferry, then in Virginia. He hoped to seize weapons and start an uprising of enslaved people. The raid failed within days. U.S. Marines and local militia captured Brown. Virginia convicted him of treason and other crimes, and he was hanged in December 1859.

Reactions were sharply divided. Many white Southerners took the raid as proof that Northerners wanted a violent slave uprising, and they blamed the Republican Party, although most Republican leaders condemned the raid. Some Northern abolitionists praised Brown as a martyr, while many other Northerners condemned the violence. The raid showed how deep the distrust between the sections had become.

The election of 1860 and secession

The presidential election of November 1860 took place in a country already deeply divided. The Democratic Party split along sectional lines, and four candidates competed: Abraham Lincoln for the Republicans, Stephen Douglas for Northern Democrats, John C. Breckinridge for Southern Democrats and John Bell for the Constitutional Union Party. The Republican platform opposed the expansion of slavery into the territories. Lincoln said he would not interfere with slavery in the states where it already existed, but he believed that slavery was wrong and should not spread. He won the presidency by winning almost all of the Northern free states. He received less than half of the popular vote and did not win a single Southern state, but he won a clear majority of the electoral votes.

To many Southern leaders this was the outcome they had feared: a president elected with no Southern support, from a party committed to stopping slavery's spread. South Carolina's convention voted to secede on December 20, 1860. By February 1, 1861, six more states had followed: Mississippi, Florida, Alabama, Georgia, Louisiana and Texas. In February 1861 delegates from the seceding states met in Montgomery, Alabama, and formed the Confederate States of America, with Jefferson Davis as president.

People tried to save the Union with new compromises. In December 1860 Senator John J. Crittenden of Kentucky proposed extending the 36°30′ line to the Pacific, with slavery protected south of it. Lincoln and the Republicans rejected the plan because it would have allowed slavery to spread, and it failed.

Why did the states leave? Several of them said so in their own words. South Carolina, Mississippi, Georgia and Texas each issued a declaration of causes. These documents named the protection of slavery as a main reason for leaving the Union. Their complaints included that Northern states had not enforced the return of people who escaped slavery, that Northerners attacked slavery as wrong, and that the country had elected a president whose party, they said, was hostile to slavery. In March 1861 the Confederacy's vice president, Alexander H. Stephens, said in a speech that the new government rested on the idea that Black people were not equal to white people and that slavery was their natural condition. That idea was racist and false, but the speech shows what he said the Confederacy stood for. Statements like these, made at the time by the people who took the decision, are key evidence for the central cause.

Fort Sumter and the start of the war (April 1861)

Lincoln took office on March 4, 1861. In his inaugural address he said he would not interfere with slavery where it existed, that no state could lawfully leave the Union, and that he would hold federal property. Fort Sumter, a federal fort on an island in Charleston Harbor, South Carolina, was still held by U.S. troops, and its supplies were running low. Lincoln decided to send supplies of food, and he told South Carolina's governor that no troops or weapons would be landed if the supplies were not resisted. Before the supplies arrived, on April 12, 1861, Confederate guns opened fire on the fort. Its garrison surrendered on April 13. This was the start of the Civil War.

Lincoln then called for 75,000 volunteer soldiers. After his call, four more slave states of the Upper South (Virginia, Arkansas, North Carolina and Tennessee) seceded and joined the Confederacy, for eleven in all. Four other slave states stayed in the Union. They were called the border states.

Other factors, and why “states' rights” is not a separate cause

Tariffs. A tariff is a tax on imported goods. Northern manufacturers generally favored high tariffs to protect them from foreign competition, and many Southerners, who bought imported goods and sold cotton overseas, opposed them. In 1832 South Carolina declared the federal tariffs of 1828 and 1832 void inside its borders, and that dispute ended without war. By 1860 the tariff was a smaller issue. Congress lowered tariff rates in 1857, and the higher Morrill Tariff, which had passed the House in 1860, became law only in March 1861, after seven states had already left the Union. Georgia's declaration of causes also complains about tariffs and other federal economic policies, but like the declarations of South Carolina, Mississippi and Texas, it gives slavery the central place.

Sectional politics. The North grew faster than the South, so its population and its number of seats in the House of Representatives grew larger. By 1860 there were 18 free states and 15 slave states. Southern leaders feared losing control of Congress and the presidency. This mattered mostly because of what it meant for slavery: the side with the votes could make the rules for the territories.

Competing views of federal power (“states' rights”). Americans of the time argued about whether Congress could limit slavery in the territories and whether a state had the right to leave the Union. Southern leaders often argued that states had the right to decide matters for themselves. People really did make this argument. But look at how it was used. In the sources of the time it is tied closely to the right to hold enslaved people: in the declarations of several seceding states, the rights being defended are the rights of slaveholders. And it was not applied the same way every time. The Fugitive Slave Act of 1850 was a strong federal law that Southern leaders wanted enforced everywhere, including in Northern states, while some Northern states passed their own laws to resist it. So “states' rights” was an argument used in the era, not a separate cause of equal weight. The useful question is “whose rights, and to do what?” In 1860 the answer was most often the right to hold enslaved people.

Putting it together

Follow the thread. The North and South built different economies, and one rested on slavery. As the country grew west, every new territory raised the same question. Compromises delayed the answer but did not settle it. Then events raised the tension: the Fugitive Slave Act, a persuasive novel, the Kansas–Nebraska Act and the fighting in Kansas, the Dred Scott decision and John Brown's raid. Throughout, enslaved people resisted, and Black and white abolitionists kept slavery in public view. In 1860 the election of Lincoln was the trigger for secession, and in April 1861 the attack on Fort Sumter was the trigger for war.

Historians still debate whether the war could have been avoided, because people made choices at each step. What the textbook consensus holds is the central cause: slavery, and the fight over its spread.