So much recent research and testing has shown that children are much, much safer in rear-facing configuration. In fact, the safety experts heralded the introduction of a new mini-van a year or so ago, in which the second row of seats turn around so the kids can play a game with the kids in the third row. I have been told that a child *not even in a car seat* is safer with that seat turned-around! As long as your child has not outgrown the weight and length limits of his rear-facing seat, the recommendation is to keep them rear-facing as long as possible. (I only made it to 18 months with both my kids.)
In the state of Illinois, there are NO set weight or age requirements for rear-facing or front-facing. The law simply states that a child must be properly restrained. That's it.
I believe the American Academy of Pediatrics has recommended leaving children rear-facing until 30 months of age (assuming the child is in the appropriate seat for his weight/length). You may want to google this to double-check.
Here's the actual wording from the State of Illinois:
Infants and Toddlers
Illinois law requires all children to be properly restrained in a child safety seat or booster seat until age eight. After age eight, Illinois law requires everyone under the age of 19 to be properly restrained anywhere in the vehicle. Currently, Illinois law does not require children to ride rear-facing to a set weight or age like some states. Illinois law does require that all children be properly restrained in child safety seats. The American Academy of Pediatrics and NHTSA strongly recommend that children stay rear-facing until they are BOTH over one year of age AND over 20 pounds to protect their fragile head, neck, and spinal cord.
More information on infant child safety seat safety
More information on forward-facing child safety seat safety
Illinois Child Passenger Protection Act
For more information regarding the state of Illinois car seat laws and guidelines, visit:
http://www.buckleupillinois.org/illaw.html