What was the impact of the Dred Scott decision on the Civil War?

The Dred Scott decision was in and of itself a huge push towards the Civil War in that it imposed a judicial law based on a political problem. It denied the earlier Missouri Compromise of 1820, and by invalidating this legislation caused the North and South to become further divided. The tension increased, and escalated. The South defended the decision and slavery in essence, while the North vehemently denounced it. There really was no breaching the divide at this point. The line had been drawn and no amount of talk could calm the storm. Only a long bloody conflict could solve the issue and after many years provide some solace to the open wound. The decision itself is said to have been one of the worst mistakes in judicial history.

In what is understood as one of the worst decisions the Supreme Court ever made, in Dred Scott, the court determined three things: first, that living in a free state did not make a slave free, second, that a slave could not be a national citizen of the United States—a freed slave could, however, be the citizen of a particular state—and that the Missouri Compromise was unconstitutional.
This decision further polarized an already deeply divided nation. Slave owning white southerners were pleased, but abolitionists and many northerners were outraged, not only at the decision, but at what seemed like judicial overreach. Maine passed legislation, for example, providing former slaves with state citizenship while Ohio passed laws saying any slave living in the state was freed: the backlash, in other words, was intense.
The decision was reached in 1857. Four years later, the country was embroiled in the Civil War. The decision solved nothing but instead increased tensions and led both sides to dig in all the harder until a war ensued.