It finally happened today---"BOB-FM" is no more. 105.9 is now billing itself as "The Rig." Never heard an odd name like that for a country station---from what i've heard so far---all automated AND BORING.
The area north of Tulsa in Oklahoma has had a "K-Rig" for over 20 years on two different frequencies. Whether on 94.3 or 104.9, you've never been able to get it in Tulsa, but you've never had to get too far out of town to start picking it up. Unlike the truck reference crainbebo mentioned, "K-Rig" in Oklahoma uses an oil rig in its logo since Tulsa was, for years, known as the "Oil Capitol." I'd guess The Rig in Bismarck is based more on the oil rig than the semi because of North Dakota's booming oil-based economy.