The economic and social influences that contributed to the Civil War were just months from turning into America’s deadliest conflict. Congress was carefully balancing slave states and free states as it admitted new territory, hoping to avoid a conflict — but the Kansas-Nebraska Act said that Kansas could make its own decision by popular vote.

That wouldn’t have been a problem necessarily, except that Missouri was a slave state. When the voting began, Missourians snuck across the border to cast votes and sway the election — in fact, enough of them snuck over the border that they were able to flip the state. When Kansas pioneers noticed, they decided to repeat the election.

The result was two mirror governments in two mirroring capitols that each drew up a constitution and an application for statehood and then sent those applications to Congress. But this was no mere battle of words, it quickly devolved into a bloody conflict. Both sides murdered, killed, and burned down neighboring towns, earning the state the title “Bleeding Kansas.”

[This was the warm-up to the Civil War, which was also fought over slavery. I wrote about it a month ago when Nikki Haley fumbled a stupidly easy question. — Ed]