Back in the 70's, many American cars had them in the rear, either behind the license plate, or above it. That included most or all fullsize cars, and many mid size ones too. I remember that if you had a full load in the trunk and it was sagging, it was difficult to fill the tank all of the way because of how low the fillers were. If the station had any kind of slope at the pumps, you had to make sure to pull in so you were pointed downhill.