The Missouri Compromise is a legislation that was passed in 1820. This established that Maine was to be admitted to the United States as a free state, while Missouri was to be admitted as a slave state. The passage of the act was significant as it legally established the idea of a balance of power between the North and the South.
The Compromise of 1850 mainly dealt with the question of whether the territories acquired in the Mexican-American War were to be considered slave or free states. The Compromise also contributed to setting Texas's borders and dealing with fugitive slaves and the slave trade.
The Kansas-Nebraska Act was a piece of legislation passed in 1854 which allowed people in Kansas and Nebraska to decide whether they would like to allow slavery within their territory. This was effectively a repeal of the Missouri Compromise of 1820. It led to conflict between the pro-slavery and the anti-slavery sectors of the population.