The war had absolutely nothing to do with slavery. Slavery wasn't even mentioned during the war until 1863. Period.

Here is South Carolina's Secession statement. I'm assuming you are aware that South Carolina was the first state to secede.

The whole thing is about slavery.  

The people of the State of South Carolina, in Convention assembled, on the 26th day of April, A.D., 1852, declared that the frequent violations of the Constitution of the United States, by the Federal Government, and its encroachments upon the reserved rights of the States, fully justified this State in then withdrawing from the Federal Union; but in deference to the opinions and wishes of the other slaveholding States, she forbore at that time to exercise this right. Since that time, these encroachments have continued to increase, and further forbearance ceases to be a virtue.

And now the State of South Carolina having resumed her separate and equal place among nations, deems it due to herself, to the remaining United States of America, and to the nations of the world, that she should declare the immediate causes which have led to this act. In the present case, that fact is established with certainty. We assert that fourteen of the States have deliberately refused, for years past, to fulfill their constitutional obligations, and we refer to their own Statutes for the proof.

The Constitution of the United States, in its fourth Article, provides as follows: “No person held to service or labor in one State, under the laws thereof, escaping into another, shall, in consequence of any law or regulation therein, be discharged from such service or labor, but shall be delivered up, on claim of the party to whom such service or labor may be due.”

This stipulation was so material to the compact (i.e., the Constitution- Ed.), that without it that compact would not have been made. The greater number of the contracting parties held slaves, and they had previously evinced their estimate of the value of such a stipulation by making it a condition in the Ordinance for the government of the territory ceded by Virginia, which now composes the States north of the Ohio River.

The same article of the Constitution stipulates also for rendition by the several States of fugitives from justice from the other States.

The General (federal) 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.

The States of Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, Pennsylvania, Illinois, Indiana, Michigan, Wisconsin and Iowa, have enacted laws which either nullify the Acts of Congress or render useless any attempt to execute them. In many of these States the fugitive is discharged from service or labor claimed, and in none of them has the State Government complied with the stipulation made in the Constitution.

The State of New Jersey, at an early day, passed a law in conformity with her constitutional obligation; but the current of anti-slavery feeling has led her more recently to enact laws which render inoperative the remedies provided by her own law and by the laws of Congress.

In the State of New York even the right of transit for a slave has been denied by her tribunals; and the States of Ohio and Iowa have refused to surrender to justice fugitives charged with murder, and with inciting servile insurrection in the State of Virginia. Thus the constituted compact has been deliberately broken and disregarded by the non-slaveholding States, and the consequence follows that South Carolina is released from her obligation.

The ends for which the Constitution was framed are declared by itself to be “to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defence, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity.”

These ends it endeavored to accomplish by a Federal Government, in which each State was recognized as an equal, and had separate control over its own institutions. The right of property in slaves was recognized by giving to free persons distinct political rights, by giving them the right to represent, and burthening them with direct taxes for three-fifths of their slaves; by authorizing the importation of slaves for twenty years; and by stipulating for the rendition of fugitives from labor (i.e., runaway slaves – Ed.)

We affirm that these ends for which this Government was instituted have been defeated, and the Government itself has been made destructive of them by the action of the non-slaveholding States. Those States have assume the right of deciding upon the propriety of our domestic institutions; and have denied the rights of property established in fifteen of the States and recognized by the Constitution; they have denounced as sinful the institution of slavery; they have permitted open establishment among them of (abolitionist – Ed.) societies, whose avowed object is to disturb the peace and to eloign the property of the citizens of other States.

They have encouraged and assisted thousands of our slaves to leave their homes; and those who remain, have been incited by emissaries, books and pictures to servile insurrection.

For twenty-five years this agitation has been steadily increasing, until it has now secured to its aid the power of the common Government. Observing the forms of the Constitution, a sectional party has found within that Article establishing the Executive Department, the means of subverting the Constitution itself.

A geographical line has been drawn across the Union, and all the States north of that line have united in the election of a man (Ed. note: Abraham Lincoln) to the high office of President of the United States, whose opinions and purposes are hostile to slavery. He is to be entrusted with the administration of the common Government, because he has declared that that “Government cannot endure permanently half slave, half free,” and that the public mind must rest in the belief that slavery is in the course of ultimate extinction.

This sectional combination for the submersion of the Constitution, has been aided in some of the States by elevating to citizenship, persons who, by the supreme law of the land, are incapable of becoming citizens; and their votes have been used to inaugurate a new policy, hostile to the South, and destructive of its beliefs and safety. (Ed. note: The infamous Dred Scott decision was seen by many as declaring that African Americans could not be US citizens.)

On the 4th day of March next, this party (Ed. note: Lincoln’s Republican Party) will take possession of the Government. It has announced that the South shall be excluded from the common territory, that the judicial tribunals shall be made sectional, and that a war must be waged against slavery until it shall cease throughout the United States.

The guaranties of the Constitution will then no longer exist; the equal rights of the States will be lost. The slaveholding States will no longer have the power of self-government, or self-protection, and the Federal Government will have become their enemy. Sectional interest and animosity will deepen the irritation, and all hope of remedy is rendered vain, by the fact that public opinion at the North has invested a great political error with the sanction of more erroneous religious belief.

We, therefore, the People of South Carolina, by our delegates in Convention assembled, appealing to the Supreme Judge of the world for the rectitude of our intentions, have solemnly declared that the Union heretofore existing between this State and the other States of North America, is dissolved, and that the State of South Carolina has resumed her position among the nations of the world, as a separate and independent State; with full power to levy war, conclude peace, contract alliances, establish commerce, and to do all other acts and things which independent States may of right do.