A lot of issues caused tensions to finally boil over into war. Slavery was at the heart of them, but on its own it was certainly not the cause of the Civil War. It was really a combination of several factors (both long term and short term) that caused war to break out in 1861.
Long term causes:
Debates over slavery + westward expansion + regional economic differences + fear/anxiety
Before the Civil War, cash crops (like cotton, indigo, tobacco) dominated the South. That’s pretty much all southern elites cared about. That and keeping slavery legal. Back then they didn’t have the farming technology we have now, so growing cash crops was very labor intensive. And white southern elites were quite fond of their cheap labor force.
Outside of the South, cash crops weren’t being grown, and slavery wasn’t popular. The northern U.S. relied mostly on manufacturing, and the West was largely agricultural (but large-scale crops did not thrive in the hard, rocky soil). Those economic differences allowed people outside the South to see slavery for what it was – a terrible and racist way to treat other human beings.
To recap so far: The North, South, and West were different economically, and only the South supported slavery.
In addition to tensions arising from those sectional differences, the U.S. was getting bigger. That expansion caused another set of problems.
Maps demonstrating the growth of the United States.
Every time a new territory or state was added, people had to decide whether or not slavery would be allowed there (because the framers of the U.S. Constitution “conveniently” left out whether or not slavery was legal). This was a real point of contention, because, as you probably know, every state gets two senators and at least one congressperson in the House of Representatives. The South was fearful that if too many “free” states were added, they would lose voting power and Congress would abolish slavery one day.
So, a series of compromises were made for decades before the Civil War actually happened. In 1820 the Missouri Compromise established a pattern of states entering the union as pairs (one free and one slave). Then in 1850, when California was the only state ready to enter, the Compromise of 1850 allowed them to enter as a free state, strengthened fugitive slave laws*, established popular sovereignty (the people living there get to decide whether or not to allow slavery) in the new Utah and New Mexico territories, and abolished the slave trade in Washington, DC. And it solved a border dispute too. You see, these compromises were getting more and more complicated.
As the 1850s wore on and the U.S. continued to grow, popular sovereignty was used more and more by Congress to “solve” the free vs. slave issue. However, popular sovereignty led to unrest and violence (Bleeding Kansas, for example) in newly forming territories. And it wasn’t just that. Widespread outrage over the Dred Scott decision, passionate responses to the Lincoln-Douglas debates, and many other events made white southern elites more and more fearful that the United States would one day put and end to slavery.
Short term causes:
Election of President Abraham Lincoln -> Secession of southern states -> Standoff at Fort Sumter -> Civil War
By the time the presidential election of 1860 rolled around, regional tensions were about to boil over. Lincoln did not say he would put an end to slavery if he was elected. He actually said he would not do that, but it was known by all that he was against slavery and he didn’t want it to spread to any new areas. In the months after Lincoln was elected president, South Carolina and six other states in the Lower South seceded from the Union.
Those seven states set up a new government called the Confederate States of America and began to act as their own separate nation. President Lincoln refused to acknowledge their new government. He firmly stood by his belief that states did not have the power to secede under the U.S. Constitution, and therefore the Confederacy did not actually exist.
A few months went by peacefully, with both sides in denial. And then everything came to a head at Fort Sumter. United States forces were occupying the South Carolina island fort, because President Lincoln stood by the fact that Fort Sumter (and everything else in the South) was still part of the United States. Confederate forces set up outside the fort, refusing to allow any traffic in or out of the fort.
By April of 1861, the U.S. troops at Fort Sumter were running out of supplies, and Lincoln announced that he was going to send in more troops to resupply the fort. The Confederate army warned Lincoln they would fire shots at any U.S. troops trying to enter the fort. Lincoln did not want war, but he had vowed to preserve the union. He could not follow the orders of a rebellious army. He sent in the troops to try and restock the fort, the Confederate army fired shots, U.S. troops returned fire, and the Civil War began. As shown in the previous map, four more southern states seceded after the shots fired at Fort Sumter.
There was no official declaration of war by Congress, because that would involve recognizing the Confederacy as a separate government. However, war was waged from 1861 until 1865, when Robert E. Lee surrendered to Ulysses S. Grant at Appomattox Courthouse.
The Civil War happened because President Lincoln vowed to preserve the union, and eleven of his states tried to leave the union. They had left over fears that their economy/way of life (slavery) would be ended, but ironically the Civil War itself caused slavery to end. It was not originally a war fought to end slavery, but that was a very happy side effect.
To be crystal clear – the Civil War was fought to preserve the union (not to end slavery).
And that’s history!
– Mrs. Lemons
* Laws that required people to return escaped slaves to their owners.