Illinois state law indicates that we have no statewide size limit on largemouth bass. We do have laws that are specific to a water body (site specific regulation) as well as how you take largemouth bass. I cannot say you took the bass legally since I don't know where you were fishing. I would be careful and read up on special laws in Cook county since that county is crazy.
It's really important to brush up on the law before you take fish from the wild and especially before you post about it on the internet.