Depends on who they are.... if they are from overseas or the coasts, I might say near Chicago. Beyond that they may have no idea where Peoria is.

Well, it all started one day in a certain part of my father's anatomy...
Thank God...now I have the table to myself.

Peoria, Illinois

Would whip out my phone and pull up a map, then show them the location of Peoria.
Would probably bore them to death describing it!

When I used to work trade shows my standard response was Peoria, which is about halfway between St. Louis and Chicago. Of course there was one foreigner, from Taiwan; a supplier of ours no less, who would proclaim in his excitable broken english, Illinois! Chicago!Yes, Chicago I'd have to answer because it was really not worth trying to explain. Thank god we don't live in southern Illinois. No wonder why they hate everyone north of I64.