What are three events that occurred between 1857 and 1859 that facilitiated southern secession

I believe the 3 events where, The Lincoln-Douglas Debate, The john brown raid and the Dred Scott Verdict. Browns raid made abolitionist (against slavery) look as if they where the bad guys, Lincoln-Douglas Made each state decide if they wanted to be a slave or no slave state and the Dred Scott made slavery 'legal' anywhere in the U.S.A. Dred Scott was 1857, Lincoln-Douglas was 1858 and John Brown Raid was 1859!

In the late fifteenth century, a major world power that established colonies in the era of old imperialism was france or germany or spain. their colonial activity was mainly limited to america or africa or asia.