My favorite is the first, that the South seceded over states' rights. Of course, that was the Southern argument when they were clinging to segregation in the 20th Century. And we still hear it from the right wing, especially in the South.
But Loewen argues that it was just the reverse at the start of the Civil War. Southern states were upset that northern states were following their own laws, rather than laws created by a federal government long dominated by Southerners - for example, that they weren't supporting slavery by returning escaped slaves.
South Carolina was further upset that New York no longer allowed "slavery transit." In the past, if Charleston gentry wanted to spend August in the Hamptons, they could bring their cook along. No longer -- and South Carolina's delegates were outraged. In addition, they objected that New England states let black men vote and tolerated abolitionist societies. According to South Carolina, states should not have the right to let their citizens assemble and speak freely when what they said threatened slavery.
Funny, huh? But the South still tries to pretend that slavery wasn't the cause of the Civil War. In reality, secession was all about slavery. You just can't get away from that.
True, the North went to war to preserve the Union, to keep the United States intact. Ending slavery wasn't their initial goal, and never the primary one. But the southern states seceded because of slavery, period. It was the election of a President who opposed slavery which initiated the whole thing.
Anything else is just trying to whitewash history.