To the OP, here's a good link I found that has all the states Rabies laws listed:
http://www.zbirdbrain.com/VAX/RabiesLaws.pdf
(I found this awhile ago when I found out I needed to know what my state's law was!!)
Hope that helps you! It looks like "Triennially" is the requirement for IL...so only every 3 years!
Here's a question, why are they coming out with 3 year vaccines when 1 year vaccines last 3 years (or more)?? My vet said they make a 3 year Rabies vaccine, but it costs like 3 times as much as the regular one. AND, if a state requires it Triennially, are they talking about the 3 year Vaccine every three years, or the regular vaccine every 3 years??