Why was segregation still practiced in southern states in the middle of the 20th century, despite the passage of constitutional amendments prohibiting segregation following the civil war? to what extent were things different in northern states, and why?

Segregation was still practiced in the south because people down there still believed in the idea of having slaves. They didn't agree with what had happened. Things were different in the northern states to a medium extent because the north never really had slaves, so they saw no reason to treat people of different color differently. I'm not saying there wasn't still some tension in the north, I'm sure there was. It just wasn't as extreme as in the south. Hope this helped. Sorry it was kinda long :)

Because of prejudice