What is considered in-state?

I am a high school senior and I've lived in Chicago my whole life. I'm trying to decide between Northwestern and USC for college. I know that many med schools have a higher in-state admission rate. By going to USC, will that grant me California in-state status? What about Illinois in-state status? Any help is appreciated, thanks.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums