Which events of the mid-1800s keep the nation together and which events pulled it apart?

An event that brought the nation together was the Missouri compromise. This compromise worked for about 30 years. This event made Missouri a slave state and Maine a free state. It also made the idea of 36 30. Anything above is free and anything below is slave. Except for Missouri witch was above. Until the Kansas - Nebraska act witch made the Missouri compromise unconstitutional. The Kansas - Nebraska act pulled the nation apart. This act made the the Missouri compromise unconstitutional and made it so the people could choose whether or not a state was slave. This basically started a land grab of who gets the most land. The South wanted Nebraska and Kansas because it was perfect for cotton. The North wanted the land so the south wouldn't get it.