You said it "caused" the Civil War and it wasn't the sole or even primary cause. But it certainly was a factor.
It's easy to focus on slavery as the main cause, due to the emotion it evokes.
Read Doris Kearns Goodwin's book "Team of Rivals". In it you will see that even Lincoln at first was not for full emancipation. His and the nations views evolved over time.
Causes Of The Civil War
What led to the outbreak of the bloodiest conflict in the history of North America?
A common explanation is that the Civil War was fought over the moral issue of slavery.
In fact, it was the economics of slavery and political control of that system that was central to the conflict.
A key issue was states' rights.
The Southern states wanted to assert their authority over the federal government so they could abolish federal laws they didn't support, especially laws interfering with the South's right to keep slaves and take them wherever they wished.
Another factor was territorial expansion.
The South wished to take slavery into the western territories, while the North was committed to keeping them open to white labor alone.
Meanwhile, the newly formed Republican party, whose members were strongly opposed to the westward expansion of slavery into new states, was gaining prominence.
The election of a Republican, Abraham Lincoln, as President in 1860 sealed the deal. His victory, without a single Southern electoral vote, was a clear signal to the Southern states that they had lost all influence.
Feeling excluded from the political system, they turned to the only alternative they believed was left to them: secession, a political decision that led directly to war.
http://www.pbs.org/opb/historydetectives/feature/causes-of-the-civil-war/
