The American Civil War was a very misunderstood historical event

American Civil War, aka War Between the States, aka the War of Northern Aggression, aka the War Between Southern Confederacy and Northern States' Federal Government.

1. First, it wasn't a civil war.

It was not a war between two parties trying to control the same government. It was an attempt of the Southern States to secede from the Union. You may say that it was a rebellion, but see the next part.

2. The Southern States had the right to secede.

The Constitution (10th Amendment) reserved all rights for the States and their people except those that were reserved for the Federal Government or were explicitly denied to the States (right to coin money, right to form international treaties, etc.). A right to secede from a union between sovereign nations is a right that was not explicitly denied to the States by the Constitution; nor was it reserved for the Federal government (a right to expel a state from the Union). Therefore, constitutionally, the States had that right.

Were the States sovereign nations before the signing of the Constitution? Historically, after the Colonies broke away from the United Kingdom, they reverted to the state of nature. Afterwards, they each re-formed into states, each with its constitution and legislature. Afterwards, the States formed a union, in which their sovereignty was preserved. (Also, what is the very last thing that you see if you look at the back of the Constitution? That's right: you see signatures of the representatives of the specific States.) The Constitution was ratified as a contract between sovereign nations and a government they were creating.

Claiming that the States had no right to secede is the same as claiming that when two people enter into a contract or a treaty (without specified time limits), they have no right to terminate the contract whenever they wish. It contradicts the accepted practices of contracts.

Therefore, the Civil War was an attempt of the Southern States to secede from the Union. It would be no different from, say, Spain deciding today that it wants to secede from the European Union and EU invading Spain to make it a "subject" of Brussels. I.e., your regular expansionist invasion.

3. Was the war about slavery?

Well, yes and no. It was in the sense that the Southern States seceded when it became clear that the Congress would be dominated by the anti-slavery Northern States. But it's not so simple as to say that the war was a crusade to end slavery in the South.

First, Lincoln and many other Northerners did not care about the slavery per se. They cared about preserving the Union. Lincoln is known for saying that if he could preserve the Union by freeing all the slaves, he would do that; if he could do it by freeing half the slaves, he would do that; if he could do it by freeing none of the slaves, he would do that too.

Many Northern abolitionists were in favor of letting the Southern states secede for three reasons: a) they did not want to be in the same Union with the states involved in the abominable practice, b) they believed (correctly) that Southern states were adamantly pro-slavery due to the reasons of honor and politics, c) they knew that the economic forces would make slavery unprofitable very soon (as they did in many other countries).

So, what was the war about? In no order of importance:

a) Southern States' rights and honor. Southerners felt that they had the right to self-government in the areas that locally concerned the individual states, not the Union altogether, and the the Federal government was abusing its powers. Plus, the Southerners felt that the Northerners were disdainful of the Southern culture and were trying to turn the Southerners into second-class citizens. (Yes, I know it's ironic for slave-owners to feel this way. I never claimed they were consistent. Many of the Founding Fathers were also slave-owners and were also inconsistent.)

b) Money. The Northern States wanted to dominate the Congress in order to be able to impose tariffs on the European imports to "protect" Northern manufactured goods. European nations, in retaliation, imposed tariffs on American exports, which were, for the most part, agricultural products (mainly cotton) from the South. So, if the Northern States controlled the Congress, they could make things favorable for the Northern manufacturers and hurt Southern farmers.

c) Northern racism and economic interests. Many Northerners wanted slavery abolished (both in the Southern States and in the Federal territories). Not all of them had humanist motives. Many of them (including the author of the famous Wilmot Proviso which would ban slavery in any territories acquired from Mexico) wanted the labor markets available for the white men.

They were 19th-century version of modern-day opponents of doing business with illegal immigrants and China. There are two reasons to oppose that today: i) one can be concerned about the welfare of the Mexicans and the Chinese, ii) one can be a racist and more concerned about "bona fide Americans" getting the jobs. The same was the case in the North in the 19th century. Many anti-slavery advocates wanted the labor markets secured for white men and former slaves shipped out of the country back to Africa or the Caribbean.

d) Southern racism and economic interest. Yes, obviously, there were Southerners who considered the slaves to be non-humans and who had interest in keeping them working in plantations, cotton gin or not. To ignore that would be intellectually dishonest.

4. Was the War worth it?

This is a complicated question. Obviously, the lives of many slaves became better off as a result of the War. There is no denying it.

Then again: the War remains the bloodiest single conflict in the US history. US remains the only Western nation to end slavery by killing a lot of its own citizens. (Even in Russia the serfdom ended around the same time peacefully.) Slavery was going to end anyway, and very soon: changing economic realities (the invention of the cotton gin, etc.) would make sure of that. Of course, the slaves might not be ok with waiting for another few decades for the markets to change, but it is not clear that all the murder of the soldiers and civilians was justified...

Economically, the War (and the ensuing Restoration) devastated the South, and its effects are still felt.

Politically, the War was a case of freeing the slaves and enslaving the free. It reversed the polarity between the Federal Government and the States. While originally, the Federal Government was a government of enumerated powers, whose sovereigns were the States (who could threaten to nullify the Government's laws if they proved to be unconstitutional or threaten to secede), after the war, it became clear that the ball was in the Federal Government's court.

The size and power of the Federal Government, its involvement in people's personal lives, in the economy, in all aspects of the society started growing and grows still. No American today is free from the tyranny of the majority, one way or another. While before, if one did not like conditions in one state, he could move to another, today, the conditions are made more-or-less uniform by the Federal tyranny. One's choice is to move to another country, which is not as easy as to move, say, from Louisiana to Massachusetts.

Effectively, whatever gains in political freedom for individuals and communities had been accomplished by the War for Independence from Britain were reversed by the Civil War.