Final answer:
The significant early battle of the Civil War that occurred in April of 1861 was the Battle of Fort Sumter.
Step-by-step explanation:
The significant early battle of the Civil War that occurred in April of 1861 was the Battle of Fort Sumter. This battle took place in Charleston, South Carolina and marked the beginning of the Civil War. The Confederate forces, led by General P.G.T. Beauregard, attacked the Union-controlled Fort Sumter, resulting in a Confederate victory.
Learn more about Battle of Fort Sumter