I am a resident of Wisconsin, but have lived in Illinois 3 years for college and 1 for work. My license and plates are still WI. What state do I file for? Do I do a NR?

Both states.

• WI resident means filing a WI resident return.
• IL income, file IL return as a nonresident.

Your resident state taxes all income but gives a credit for income taxed by another state.  Please carefully follow these directions to prepare the states in a special order. You may need to delete both states and begin again.

1. First, prepare your non-resident IL return. This creates your tax liability for the non-resident state. How do I file a nonresident state return?
2. Then prepare your resident state WI return and it will generate a credit for your income already being taxed in the non-resident state. 
3. The credit will be the lower of the state tax liabilities on the same taxable income. You may owe your resident state,  if they have a higher tax rate along with differences in how the taxable income is calculated.

It isn't possible for the program to create a credit before it knows the liability. Your returns may be wrong if you do not prepare the states in this order.

Reference: IL filing