A) Missouri was admitted to the Union as a free state. I just went over this in history, and there was a big fight between the North and South, prior to the American civil war about the expansion of slavery to the west, and how that would be settled. There had already been attempts to settle the west according to how settlers in each territory voted, but that quickly turned to mayhem and disaster. The civil war could have taken place in the 1830s over this issue, and it's uncertain what the outcome would have been. Seeking a final solution that wouldn't overly p___ off both sides, they decided that slavery could be expanded to all states south of the 38th parallel (Mason-Dixon line). Slavery was forbidden in any territory north of there. Sticky issues such as the Dread Scott case, and the Fugitive Slave act later came up and caused more turmoil and argument.
Later, the South became angry at ANY limitations on slavery, viewing the North as hypocritical in their treatment of factory workers, and trying to progress their economic agenda by boxing in Slavery. Fearing the ultimate demise of slavery in the South, 11 states succeeded from the Union. Despite Lincolns resolution to reunite the Union, he did not try to use force in doing so, and was afraid to speak out firmly on the issue of slavery until 1863. The South got uppity and fired on fort Sumter, which triggered the civil war. The North hadn't originally been looking to outlaw slavery in the South, but ended up doing so after a long and bloody struggle that lasted 4 years.
To this day, many Southerners and hillbillies claim that the civil war was about "states rights" and "not about slavery". In reality, the white people were angry that their states couldn't further impose slavery and violate human rights with out criticism from the federal government and being held accountable to them. Although 100% right about the North's hypocrisy and ulterior motives, the Souths paranoia and insistence upon white privileged is what ultimately started our civil war.
After the war, some Southerners lamented that it was the punishment of God, but many more insisted that it was a noble tragedy, and the South would rise again. Although quite controversial and not reflective of the majority of Trump voters, there is a group of them that greatly emphasized this idea in our election, and believed that he was a champion of this concept when he won the presidency. Regardless of ones beliefs in modern politics, it is important that we try to come together and reach across the aisle, as we are more divided then we've ever been in the past century and and half. It's important to study our history, and to heed the lessons there in so we don't repeat them. I guess this is a whole lot more in depth then what was needed, but I hope you've gained a much greater scope of what will hopefully remain our only civil war, and that this helped you to understand better : )