Stay away from Cabrini Green and the South Side. Cabrini Green is known as 'the projects' and is actually the place where the nightmarish tale takes place in the movie, 'Candyman.' They will be tearing it down soon, but in the meantime, stay away from that area. It is on the west side of Halsted St. The south side is anything south of the Loop. Definitely NOT the kind of place you want to be stuck in, especially at night!
Avoid Cabrini Green and most of southside. Chicago might appear as a safe city, but there are dozens of so called islands in the city, where living is safe but outside of it is not. Take for example University of Chicago. It is safe, but the surrounding neighborhoods are very dangerous.
There are a lot of gangs in Chicago, but they usually quarrel amongst themselves. If you're not looking for trouble, you won't find it.
Update: Cabrini Green doesn't really exist anymore, since the area is now 'class-elevated' by expensive new condominiums and strip malls.
Caution is the key here. Like any big city, you should use common sense and try to avoid any area which is dark and isolated. Be aware of your sorroundings and always have your money in a safe place (money belt, bra?). What I usually do is know exactly where I am going, how to get there and if I am taking the metro, have my ticket in hand. Pickpocketers are found in every major city, so being alert is your best bet. Leave expensive jewelry at home and never carry more money then you need. Leave your passport and extra cash and travelers checks at the hotel safe. If you are staying at a hostel, I would recommend that you carry your important belongings in a seperate small bag, pack or shoulder bag. Make sure you have copies of your passport and numbers of travelers checks (if you carry these) in a seperate location for just in case they are lost or stolen. The number to your local authorities is a good idea.
it is a big city, need to say more???
Well maybe as a comfort, I didn't feel unsafe at all in Chicago, felt pretty safe actually.
This is the jail in downtown Chicago. You do not want to end up here. So be nice and don't break the law.