It is beyond any doubt that slavery was the driving cause of the Civil War. Any doubt about that can be erased by reading the Confederate Constitution (and the constitutions of the 13 states forming that confederacy). All of them make it clear that they seceded because of a belief in the supremacy of Whites and the desire to continue slavery in those states. That was not doubted at that time by citizens of either the North or the South.
But the residual racism that still exists in this country has many people trying to rewrite history to justify their own perverse beliefs. They would tell us that the Civil War was fought over states' rights (ignoring the fact that the only state right in question was the right to own slaves). And sadly, too many Americans are eager to accept this rewriting of our history -- about 29% say slavery was not the cause of the Civil War, and another 14% say they are unsure.
That means only 57% (less than 6 out of 10 people) is willing to accept historical fact. I guess I should be grateful that a majority of Americans understand our history, but I'm not. It's troubling that 43% are not willing to accept that. And it shows that this country still has a serious race problem -- with too many still wanting to justify slavery (i.e., racism).
Note especially that half (50%) of Trump voters say slavery was not the cause of the Civil War, while only 43% were willing to admit it was. That makes clear what many of us have claimed -- that racists flocked to support Trump (who they considered to be one of their own).
These charts reflect the results of a new Economist / YouGov Poll -- done between November 5th and 7th of a random national sample of 1,500 adults, with a 3.2 point margin of error.