"In the momentous step which our State has taken of dissolving its connection with the government of which we so long formed a part, it is but just that we should declare the prominent reasons which have induced our course. 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. "
Looks like the rebels disagree with you. They say it was slavery, not tarrifs.
Oh really? Four states did declarations of causes when they seceded. You cited one, Mississippi, and concluded that the whole of the south therefore "disagrees" with the assertion that the tariff was an issue. For the record, I do not consider an issue to have been the sole issue of an inherently complex war and consider it foolish to make attempts to simplify an irreducably complex conflict to single issues such as slavery, as northern apologists often do. That being said, the issue of the tariff itself was indisputably high among the many causes of the war. Two of those four states that drafted declarations of causes cited it among them - Georgia and Texas. Texas listed it as a point among many. Georgia discussed it at length over several paragraphs composing a major part of their declaration.
Georgia, A Declaration of Causes of Secession, January 29, 1861:
"The material prosperity of the North was greatly dependent on the Federal Government; that of the the South not at all. In the first years of the Republic the navigating, commercial, and manufacturing interests of the North began to seek profit and aggrandizement at the expense of the agricultural interests. Even the owners of fishing smacks sought and obtained bounties for pursuing their own business (which yet continue), and $500,000 is now paid them annually out of the Treasury. The navigating interests begged for protection against foreign shipbuilders and against competition in the coasting trade. Congress granted both requests, and by prohibitory acts gave an absolute monopoly of this business to each of their interests, which they enjoy without diminution to this day. Not content with these great and unjust advantages, they have sought to throw the legitimate burden of their business as much as possible upon the public; they have succeeded in throwing the cost of light-houses, buoys, and the maintenance of their seamen upon the Treasury, and the Government now pays above $2,000,000 annually for the support of these objects. Theses interests, in connection with the commercial and manufacturing classes, have also succeeded, by means of subventions to mail steamers and the reduction in postage, in relieving their business from the payment of about $7,000,000 annually, throwing it upon the public Treasury under the name of postal deficiency. The manufacturing interests entered into the same struggle early, and has clamored steadily for Government bounties and special favors. This interest was confined mainly to the Eastern and Middle non-slave-holding States. Wielding these great States it held great power and influence, and its demands were in full proportion to its power. The manufacturers and miners wisely based their demands upon special facts and reasons rather than upon general principles, and thereby mollified much of the opposition of the opposing interest. They pleaded in their favor the infancy of their business in this country, the scarcity of labor and capital, the hostile legislation of other countries toward them, the great necessity of their fabrics in the time of war, and the necessity of high duties to pay the debt incurred in our war for independence. These reasons prevailed, and they received for many years enormous bounties by the general acquiescence of the whole country. But when these reasons ceased they were no less clamorous for Government protection, but their clamors were less heeded-- the country had put the principle of protection upon trial and condemned it. After having enjoyed protection to the extent of from 15 to 200 per cent. upon their entire business for above thirty years, the act of 1846 was passed. It avoided sudden change, but the principle was settled, and free trade, low duties, and economy in public expenditures was the verdict of the American people. The South and the Northwestern States sustained this policy. There was but small hope of its reversal; upon the direct issue, none at all. All these classes saw this and felt it and cast about for new allies. The anti-slavery sentiment of the North offered the best chance for success. An anti-slavery party must necessarily look to the North alone for support, but a united North was now strong enough to control the Government in all of its departments"
That was Georgia, taking issue with protectionism at length and in great detail. As I noted, Texas asserted the issue as well among its causes:
A Declaration of the Causes which Impel the State of Texas to Secede from the Federal Union. February 2, 1861
"They have impoverished the slave-holding States by unequal and partial legislation, thereby enriching themselves by draining our substance."
And if you still dispute the inescapable fact that the tariff issue was a major cause in the war, why not look at the word of one of your own? The following excerpt comes from an eyewitness account to the secession crisis. Its author, himself a prominent participant in Lincoln's policy at the time, openly admits at least three major disputes were occuring before Congress in the winter of 1860-61, and concedes that Lincoln intentionally worked to make sure the public debate was frame around slavery. With my emphasis added...
"Mr. Lincoln arrived in Washington and took up the reigns of control. It soon became very evident that, so far as the Republican party is concerned, secession if properly managed is rather a benefit than a misfortune. Anti-slavery was the only ground on which it could act with anything like unanimity. In ordinary times, the tariff bill would have broken it down, and even under the tremendous pressure of disunion, the struggle over the Cabinet shook it to its very center. On all questions except that of slavery it can never act together with any reliable degree of concert, made up as it is of incongruous elements freshly and roughly joined together." - Henry Adams, March 1861
In case you do not know your history, Henry Adams was the son of Congressman Charles Francis Adams, son of the former president and a main Lincoln ally during the secession crisis.