I wanted to separate that GIF, and then continue with a link showing the boundaries of the "Chicago Center" ARTCC.
http://skyvector.com/?ll=43.271206114680936,-88.04498290896113&chart=304&zoom=4
If you wish to open the link, then navigate within it in the same way as one would with 'Google Maps' (IOW, scroll with the center mouse wheel to Zoom In/Out, click and hold to Slew, etc) you will see the boundaries that define the different ARTCC sectors. And, how well it comports with the blank area, in the GIF above.
For instance, just north of the O'Hare Airport, cutting across Lake Michigan, you see a light blue rather jagged line...labelled "Chicago" on one side, and "Minneapolis" on the other. This is one boundary example.
Of course, there is also this handy image, obtained from the InterWebs:
