One of my favorite old gas stations is at 1149 Elkhorn, Belle Fourche, SD. For a number of years it was the site of Bobby Whittaker's Motorcycle campground. The owner was an antique motorcycle enthusiast. His campground was favored by Moto Guzzi riders, Brit-bike enthusiasts, and the like, and as such the patrons and the bikes were a lot more interesting than the typical rally crowd. They kept tools and a repair stall available for the use of campground guests.
The building was a classic old stucco station with a covered forecourt. Behind the station, the ground sloped down to the cottonwood-shaded bottoms of the Redwater River, not too far from where it flows into the Belle Fourche. Lots of nice tent spaces. In inclement weather, you could shelter your bike under the US 212 bridge.
Street level photos are proving hard to find. I don't know if the campground is still open during Rally Week; last time I was through there was in June a couple of years ago and the place looked pretty sleepy.