Steunenberg, ID was only a click away on Historical Maps of Idaho once I knew to look for it. To explore further, I would really recommend using that site and their map viewing tools. Thanks to those of you that are out there skowering the countryside for more information.
Finding the town on maps and Mark sharing his Steunenberg postmark has been quite a treat. Now an old photograph or picture postcard that might have been taken and survived the town's demise would be really cool.