Ah thanks.
I also recall reading that it voted around 45% for George HW Bush in 1988. It wasn't as Democratic as a district as everyone speaks of it back then. I mean Democratic enough to vote for any Democrat who wasn't a blatant criminal maybe, but that wasn't the case. Cao actually won a far bigger upset. That was more like if Tom DeLay stayed in the race in 2006 but was still defeated by Lampson.
Back in 1988 it contained Southern Cook County IIRC, and was far more suburban and therefore competitive than it is now. Back then the 1st and 7th Districts covered most of the South side, and the former was over 80% black.