Who started the America Civil War?

Answer 1

The first shots were fired by the Confederates, who were not wanting a war, but who were asserting their self-proclaimed rights over an island in Charleston harbour that was still occupied by US troops. (The Confederate commander was General P.G.T. Beauregard.)

Another answer might be to identify the individual whose actions divided the two sections so radically that war became inevitable.

This could be Harriet Beecher Stowe, whose best-selling book 'Uncle Tom's Cabin' recruited many Northerners to the cause of Abolitionism, and generaly heated-up the debate.

Another could be John C. Calhoun, although long dead. He was the South Carolinian who encouraged the South to defy Federal Laws and withhold the high taxes on cotton.