While the north and south had differences, The compromise of 1850 intensified their political differences between the two. With the Compromise making California a free-state, enforcing a more effective slave laws, and the principle of popular sovereignty, making the south unhappy. The south didn't see this as an equal compromise and wanted California to be a slave state and that believed that the compromise was unjustified and favor of the north. Each side also believed that the idea of popular sovereignty would not work and would only lead to more term oil between the two. The conflict would only increase with the election of Lincoln in the 1860 election causing the southern states seceding from the Union to from their own confederate states. which lead the Civil War, a mouth later after his inauguration as president of the United Sates.
The North and South had two different economic system. The North's economy was mostly industrial, building ships, fishing,and lumber. The South economy was agriculture based, farming cotton, tobacco, wheat, corn, and livestock The South economy was dependent of the free labor of slavery. The north was heading in the other direction by industrializing their economy and viewed slavery as immoral and no longer need for economic purposes. Which created conflict between the two side on how their economies should run.
The south believed in slavery and that each state should be independent and govern itself. The north were anti-slavery and believed that all the states be United and governed by one central government. The people of the south also believed that people of the north were given more rights then they were given. Which created more conflict between the two sides leading to the south separation from the Union.
While their isn't one specific event causing the war. There are many events that should be look at as triggering events. First the compromise of 1850 which made the California a free-state and not a slave state. Lincoln unwillingness to compromise with the south about slavery in the states. Which to the south secession from the Union. The battle at fort sumer's is consider by many to be the start of the Civil War. The battle was the first major battle between the Union and the confederates that was won by the confederates and created controversy in the north causing the north to take more military actions towards the south and starting the war.