In the spring of 1861, the United States of America split into two hostile countries—the United States and the new Confederate States of America. The two...
Compromise of 1820 - Admitted Maine to the Union as a free state and Missouri as a slave state, but prohibited slavery in all other parts of the Louisiana Purchase north of 36' 30'
Compromise of 1850 - Admitted California as a free state, but allowed voters in Utah and New Mexico territories to decide if they wanted slavery
Kansas-Nebraska Act, 1854 - Allowed voters in Kansas and Nebraska territories to decide about slavery.