Please no derogatory remarks here but what is this all about?

I went to a friend's house for the game yesterday in Edmond and some people came and they kept referring to themselves as 'southsiders' ... not wanting to appear really clueless, I was asking them what the boundaries are and what does they really mean? They had a few choice descriptions some of which included racial slurs... (I didn't know people still talked like that in normal conversation). I was trying hard not to flinch and told them I hadn't heard those words in a long, long time since I moved from CA ( which went over really well.. lol )

I was just wondering about the whole northside/southside issue.

Southsiders - Northsiders? Where did this come from?