1. Slavery. In the south there were many big plantations, and they needed a lot of workforce. They took slaves from Africa, and they forced them to work at the plantations
2. Slavery was ruled unconstitutional, which means that it is unauthorized by the constitution, or is inconsistent with the constitution
3. Obama didn't root himself in the Civil Rights Movement, something that removed the "us versus them" mentality completely. He focused on relevant issues, and did not talk as if the US was made up of many populations, but as if they were one.
