No special license is required for snowmobile riders aged 16 and over. Riders aged 12 to 15 must complete a snowmobile education course before they're allowed to ride. Children aged 10 or 11 can ride under the direct control (same sled) of a parent or guardian. Kids under 10 cannot operate a snowmobile in Illinois.
Check out these Stoy, IL ATV/OHV resources: