Many events occurred before the Civil War that created a disconnect between Americans within the United States. The South believed that slave labor increased the profitability and sustainability of their economy by allowing for cheap labor that lasted a long time, while slaves could also reproduce, creating more cheap labor in the future. The North, however, did not agree with the South; they didn't want slaves to take American jobs and they also promoted American labor. The North and South each attempted to influence the other's position on the issue of slave labor, but neither budged. As time passes, certain events lead to the decline of slavery. The South recognized this and threatened to secede from the Union, increasing the disconnect between the two. Secession is defined as: breaking away from; but to the South it was leverage to help them get what they wanted or they could leave the union. The admission of free states, the prohibition of the expansion of slavery, and the election of President Lincoln were significant factors leading to the secession of the Southern states in 1860 and 1861. The union faced its first obstacle when the decision to admit states. Maine, Missouri, and newly acquired territories, known as the Louisiana Territory, applied for admission to the Union. At the time the South led the Senate in votes by a slim margin; furthermore, Maine was admitted as a free state, while Missouri was admitted as a slave state. It was also decided that no part of the Louisiana Territory would permit slave labor. The Missouri Compromise of 1820 sparked a backlash on both sides: abolitionists despised the expansion of slavery into Missouri, while pro-slavery advocates wanted more Missouri land that would allow… It seceded, and each state, one by one , separated, in the hope that slavery would be preserved. Slavery eventually died out and the Southern states seceded from the union again, but not without a civil war. Ultimately, the differences between the North and the South could not be resolved except by civil war. These causes, as well as others, left the South with no viable option, in their eyes, other than to secede from the Union, leading to the Civil War. Political, social, and philosophical conflicts combined to form the final disagreement over slavery between the two regions. Overall, the admission of a disproportionate number of free and slave states into the Union, the prevention of the expansion of slavery, and the election of President Lincoln were significant factors leading to the secession of the Southern states in 1860 and 1861.