625 ILCS 5/1-162.5: Principal place of business.

The place where any person transacts his principal business, or where he makes up and approves his payroll, maintains a central file of records and maintains his principal executive offices. In the event that not all of these functions are performed in one place, then that place where a majority of such functions are performed or the place where such person does in fact principally transact and control his business affairs.