What caused the American Civil War was the institution of slavery, which dates back during early colonial times. During the American Revolution, all men were supposedly have been created equal but slavery was still legal in all thirteen colonies. It was only a matter of time before slavery would be abolished in the north. It was still a part of the American way, protected within the body of the Constitution. Also, prior to the Civil War southerners believed that state laws should be above federal laws and they should abide by state rulings first. This issue would be called State's Rights, eventually giving southerners the mindset of sectionalism leading to Civil War.
On November 6,1860 Abraham Lincoln was elected president of the Union. Three months after his election, seven democratic states did not agree with Lincoln the republican being elected as President and decided to leave the Union. These states were Texas, Louisiana, Georgia, Alabama, Florida, Mississippi and leading the way was South Carolina.
They did not like the fact that a Republican was elected because the views of the Republican North (anti-slavery) were different than the Democratic South (pro-slavery). The election of Lincoln was they're reasoning to secede from the Union and start the Confederate States of America.
On February 18, 1861 the Confederate States of America elected Jefferson Davis as their president after adopting a constitution ten days earlier. Montgomery, Alabama became the capitol of the South and the now infamous flag the "Bars and Stars" was adopted. The name "United States of America" was considered to be dissolved by the southern states that defected from the Union. Therefore signaling that civil war was inevitable and giving Davis authorization to raise 100,000 troops.
The following month during President Lincoln's inaugural speech, he tried to avoid conflict by saying...