Was slavery the primary cause of the Civil War?

Most historians would agree that slavery was the primary cause of the Civil War, because the issue of slavery lay just beneath all of the more specific issues that led to secession.

After the war, Southerners would try to distance themselves from slavery as a cause of the war, but during the secession crisis that followed Abraham Lincoln's election, proponents of disunion openly said that they wished to leave the Union to protect slavery. In...

Most historians would agree that slavery was the primary cause of the Civil War, because the issue of slavery lay just beneath all of the more specific issues that led to secession.

After the war, Southerners would try to distance themselves from slavery as a cause of the war, but during the secession crisis that followed Abraham Lincoln's election, proponents of disunion openly said that they wished to leave the Union to protect slavery. In their "Declaration of Causes" of secession, the secession convention in Georgia pointed to "...numerous and serious causes of complaint against our non-slave-holding confederate States with reference to the subject of African slavery." Most of the other Deep South states said something similar. The first seven Confederate states left the Union because they feared that the federal government under Lincoln and the Republicans would undermine slavery in the South, or perhaps more accurately, that they would refuse to accede to Southern demands on slavery as they had done (with the exception of a few issues) in the past. So the direct cause of the war was the secession of the Southern states, and the Confederate decision to fire on Fort Sumter in April of 1861. But the cause of secession was slavery. From a Union perspective, the purpose of the war would change over time from preserving the Union to ridding it of slavery. As James MacPherson, perhaps the most respected living Civil War historian recently said in an interview about the causes of slavery:

Probably 90 percent, maybe 95 percent of serious historians of the Civil War would agree on the broad questions of what the war was about and what brought it about and what caused it...which was the increasing polarization of the country between the free states and the slave states over issues of slavery, especially the expansion of slavery.”