The US Civil War (April 12, 1861, to May 26, 1865) erupted due to differences between slave states and free states over the power of the federal government to restrict slavery in new states entering the union. Tensions had been growing for decades and were fueled by the failure of two legislative decisions, the Missouri Compromise of 1820 and the Compromise of 1850.

The Missouri Compromise attempted to balance the interests of free states and slave states in the expansion of US territory. According to the act, signed into law by President James Monroe, Missouri would be admitted as a slave state, while Maine was admitted as a free state. The act contained language that kept the remaining territory of the Louisiana Purchase (“on the parallel of thirty-six degrees of north latitude,” according to Paragraph 2 of the Missouri Compromise) from becoming “slave-holding” states. However, the Kansas-Nebraska Act of 1854 repealed the Missouri Compromise and strengthened pro-slavery initiatives. This, in turn, angered many anti-slavery and/or abolition advocates. Note that anti-slavery and abolition are not interchangeable: Anti-slavery in this context means not expanding slavery, and abolition means the eradication of slavery.

The Compromise of 1850 was, again, intended to mitigate tensions between pro and anti-slavery/abolition sentiments.