If I had to guess, I'd say the cold winters is one of the reasons Chicago wasn't listed for the Leaf - and could be why people there, or the rest of us, perceive that people in Chicago wouldn't be real pro-electric vehicle.
It'll be interesting to see the sales figures of the Ford Focus Electric vehicle in citires like Chicago compared to LA or San Francisco!
With some of the highest per gallon gas prices (next to CA), I would think that Chicago would at least be a top ten area fo EV's, our taxes (increased income tax and one of the highest sales taxes) are also high so anything that will save us money should be good -- we don't have the bitter winters of say a Fargo, ND but depending on your commute, even with a more limited range in the winter either a LEAF or Focus EV should still be an alternative.
I did come across this info on Hybrid percentages of total car registrations per 10,000 (non-home built EV's are so new I doubt we'll see anything this significant for quite a few years)http://bioage.typepad.com/.a/6a00d8341c4fbe53ef014e860c8ec0970d-popup
IL is actually above WA, TN, VA, PA and MA but way below CA (no surprise); of course just another compiling of stats but shows that IL could be considered the 5th largest target!