There was no event that sparked the beginning of the Civil War.
Here are a few reasons why the Civil War was started:
Slavery: The South wanted slaves in the future to tend their farms, but the North did not want to have slaves in the future, and often helped them escape.
Uncle Tom's Cabin: Uncle Tom's Cabin was a book written by Harriet Beecher Stowe highlighting what slavery actually is and what it's about. This really opened the eyes of many people in the North, enraging many.
The Underground Railroad: The Underground Railroad was a railroad that was used to help runaway slaves escape to the North. Abolitionists were there waiting in-case a slave owner came looking for their slave, and they would beat the slave owner.
Abraham Lincoln: Abraham Lincoln was the president who officially stopped slavery. So, when this republican was running, the South were getting very wary as to if he was going to abolish slavery or not. Which he ended up doing in the future.
Fort Sumter: Fort Sumter was awaiting supplies when the Confederate forces attempted to get Fort Sumter's General to surrender. The general refused, later after that the Confederate forces began firing at the fort, until they surrendered the next morning.
Fort Sumter was what ultimately started the Civil War.