It was the worst war in American history. It was called the Civil War, or the War Between the States, and sometimes brother fought brother and father fought son . More than 620,000 Americans died. Cities were destroyed, farms burned, homes leveled . On one bloody day at a place called Antietam, more men were killed than on any other day in all our history .

What was it all about? Why were Americans fighting Americans? When the war began, people on both sides claimed they weren't fighting over slavery. But they were fooling themselves. Most white Southerners wanted to keep slavery because they thought their way of life depended on it . The Southerners—they were also called Rebels—believed in states' rights. They thought any state should have the right to pull out of the United States. They said they were doing the same thing that George Washington and John Adams and the other revolutionaries had done against King George: fighting for their freedom. President Abraham Lincoln did not agree . He said, "We all declare for liberty, but in using the same word we do not mean the same thing. You think slavery is right and ought to be extended, while we think it is wrong and ought to be restricted."

What the South did was form its own nation. Eleven southern states seceded from the Union . They created the Confederate States of America and elected their own president and congress . They said all they wished was to go peacefully from the Union. But the Union wouldn't let them do it. Northerners said that when the states joined the Union they all agreed to uphold the Constitution, and they couldn't just pull out any time they wanted. If that were allowed, soon there would be no Union at all. Abraham Lincoln put it this way: "We must settle this question now, whether in a free government the minority have the right to break up the government whenever they choose ."