The first African slaves arrive in the Americas in 1619. The Revolutionary War reaffirms colonial independence from Britain. The Constitution establishes limits on Federal power but leaves open the question of slavery. The Missouri Compromise offers a temporary solution to slavery in the expanding US territories. Lands acquired in the Mexican War exacerbate the tensions as does the Compromise of 1850. The Dredd Scot Decision leaves an irrevocable split. Lincoln's election leads to secession of several Southern states. Opening shots are fired at Ft. Sumter.