I have been fascinated reading the defensiveness of many reviewers on Amazon who insist that slavery had nothing to do with the Civil War, resurrecting the old saw regarding states' rights, etc. It seems to me a good source for refutation of this idea is the secession documents themselves.
Georgia: "The people of Georgia having dissolved their political connection with the Government of the United States of America, present to their confederates and the world the causes which have led to the separation. For the last ten years we have had numerous and serious causes of complaint against our non-slave-holding confederate States with reference to the subject of African slavery." First sentence.
Mississippi: "Our position is thoroughly identified with the institution of slavery-- the greatest material interest of the world. Its labor supplies the product which constitutes by far the largest and most important portions of commerce of the earth. These products are peculiar to the climate verging on the tropical regions, and by an imperious law of nature, none but the black race can bear exposure to the tropical sun. These products have become necessities of the world, and a blow at slavery is a blow at commerce and civilization. That blow has been long aimed at the institution, and was at the point of reaching its consummation. There was no choice left us but submission to the mandates of abolition, or a dissolution of the Union, whose principles had been subverted to work out our ruin."
South Carolina goes on at some length about how it was a free and independent state never subject to the Constitution and then complains about the federal government's failure to enforce the Fugitive Slave Laws. In other words, the federal government failed to uphold the Constitution which it said it didn't have to abide by. "The General Government, as the common agent, passed laws to carry into effect these stipulations of the States. For many years these laws were executed. But an increasing hostility on the part of the non-slaveholding States to the institution of slavery, has led to a disregard of their obligations, and the laws of the General Government have ceased to effect the objects of the Constitution. " It then goes on to talk about how the Constitution supported the institution of slavery and it was the failure of the northern states to recognize that fact which lead to South Carolina's withdrawal.
Texas::" She was received as a commonwealth holding, maintaining and protecting the institution known as negro slavery-- the servitude of the African to the white race within her limits-- a relation that had existed from the first settlement of her wilderness by the white race, and which her people intended should exist in all future time. Her institutions and geographical position established the strongest ties between her and other slave-holding States of the confederacy. Those ties have been strengthened by association. But what has been the course of the government of the United States, and of the people and authorities of the non-slave-holding States, since our connection with them?" Texas goes on to complain that the northern states were preventing the expansion of slavery.
Judging from what the southern states themselves said, at the time, it was all about slavery. I suspect it was the Lost Cause that became politically correct, not the other way around.
Source: Official secession documents found at http://sunsite.utk.edu/civil-war/reasons.html
One might, in fact, present the argument that it was the northern states like Pennsylvania and Wisconsin who should have been screaming about states' rights since it was the southern states demanding federal enforcement of the fugitive slave laws and several northern states passing laws (most deemed unconstitutional) intended to impede that enforcement, ("see Prigg, Sanford see and federal marshals' attempted enforcement of the Compromise of 1850 and many "personal liberty cases.")
We could refocus the debate over slavery by redefining the issue as one about "property." Slaves were considered property. The Constitution protected property. Supreme Court decisions through 1857 consistently considered slaves to be property. The Founders wrote in many compromises in the Constitution to protect the rights of southern plantation owners (of which they could include themselves, most of them.) David Blight (Race and Reunion) has noted that slaves by 1860 were worth about $3.5 billion, an enormous sum then and of course the southern plantation owners didn't want to give up their property. The cotton business was booming and had doubled in value every decade for four decades before 1860. Ironically, one might posit that the southern states needed a strong federal government to enforce the Fugitive Slave Acts and it was states like Wisconsin and Pennsylvania who insisted on "states' rights by passing laws making enforcement of federal Fugitive Slave laws difficult. Southern states, in their declarations of secession documents, said the reason for secession was their desire to protect slavery (see South Carolina and Georgia esp., which also makes reference to slaves as property and their constitutional right thereto). Slavery and race have sullied this country for centuries; to whitewash it is rather sickening. As Bernard Malamud wrote in The Fixer: "There's something cursed, it seems to me, about a country where men have owned men as property. The stink of that corruption never escapes the soul, and it is the stink of future evil."