Here is an update. I was searching for potential test centers for our upcoming trip to Africa in June and came across this link.

This appears to be the same location as the walk-in center mentions in the CDA's O'Hare web sire (link). If you click on the first link and select the button for scheduling an appointment for travelers, you will get the location.

I'll keep checking in on them and probably schedule the 24 hour turn around, 48 hours in advance, Just being paranoid.