There's such a thing as selective memory, there's also a thing called selective history, and the winner usually selects the history of a war. The American Civil war is no exception.

"In summary, the South wanted independence, not the protection of slavery, and the North wanted reunion rather than abolition of slavery. This is what President Lincoln had stated in the very beginning before the war and again what he had stated near the end of the war.
It was generally recognized in both the North and the South by 1865 that slavery was a dying institution, not just in America, but throughout Western Civilization. It was also obvious to both the North and the South that slavery would be hard to maintain in a separate Confederate South without the constitutional and statutory fugitive slave provisions which had required free states to return escaped slaves. In fact, many abolitionists had advocated Northern secession before the war as a means to end slavery by depriving the Southern states of the benefits of the fugitive slave clause in the Constitution and the laws relating thereto. The offer of the North to pay for the freed slaves was merely an added inducement to rejoin the Union but Lincoln had always been willing to accept slavery where it already existed if the South would remain in, or later, rejoin the Union. The right of a state to secede clearly had been accepted in the North and the South at the time of the formation of the Union and up until the time of the War Between the States. For example, the New England states frequently asserted the right of secession and threatened to use it on five occasions: in 1803 because of President Jefferson’s Louisiana Purchase; in 1807 over the Embargo Act; in 1812 over the admission of Louisiana as a state; in 1814 at the Hartford Convention because of the War of 1812; and finally, in 1845 over the annexation of Texas.

If the agricultural South rejoined the industrial North, they would again be subject to economic exploitation of the protective tariff, which was paid primarily by the South and was by far the main tax to operate the central government in Washington, D.C. The North, due to their increased representation in Congress, was able to control where the money was spent, which was primarily for internal improvements in the North, a practice the South considered unconstitutional. The protective tariff and internal improvements had been two of the key problems between the two sections since 1828, along with the general disagreement about the size and power of the central government in Washington."

http://www.lewrockwell.com/orig2/denson6.html