Hi, I'm John Green. This is Crash Course US History, and today we discuss one of the most confusing questions in American history: what caused the Civil War? Just kidding, it's not a confusing question at all. Slavery caused the Civil War. Mr. Green, Mr. Green, but what about like states' rights and nationalism? Economics made from the past? Your senior year of high school, you will be taught American government by Mr. Fleming, a white southerner who will seem to you to be about 182 years old, and you will say something to him in class about states' rights. And Mr. Fleming will turn to you and he will say, "A state's right to what, sir?" And for the first time in your snotty little life, you will be well and truly speechless. The road to the Civil War leads to discussions of states' rights to slavery and differing economic systems, specifically whether those economic systems should involve slavery, and the election of Abraham Lincoln, specifically how his election impacted slavery. But none of those things would have been issues without slavery, so let's pick up with the most controversial section of the Compromise of 1850: the Fugitive Slave Law. Now, longtime Crash Course viewers will remember that there was already a fugitive slave law written into the United States Constitution. So what made this one so controversial? Under this new law, any citizen was required to turn in anyone he or she knew to be a slave to authorities. And that made like every person in New England into a sheriff. And it also required them to enforce a law they found abhorrent. So they had to be sheriffs, and they didn't even get little gold badges. Tappable can have a gold badge. Oh, awesome. Thank you. This law was also terrifying...