Why was it important to keep England neutral during the Civil War?

Answer 1

Initially, the tendency of Great Britain was to support the Confederacy, on the theory that as the original 13 Colonies had a right to independence from Great Britain, so the Confederacy ought to have a right to independence from the United States. If British support were actively given to the Confederacy, munitions and other resources would flow to them and it would be more difficult, and perhaps impossible to defeat them. The Union therefore needed to keep Great Britain neutral in that conflict. Once the Civil War became clearly about the abolition of slavery rather than just holding unwilling states in the Union, that became much easier because Great Britain had already abolished slavery and was actively opposing the slave trade along the African coast.