Gaz-Bah was on Wilson Boulevard (what North Main becomes as it gets near to I-20 and heads to Blythewood) right next to the long defunct Denny's restaurant, and was open until fairly recently. I'm not sure when it closed, but the branding is still up, and the gas pumps have yet to be taken out. I find it a little odd that they felt it necessary to board the store completely up, given that the aforementioned Denny's has survived in good shape for years with no apparent vandalism.
As I was taking these pictures, one of those erratic Fall flocks of birds was in the area, moving from the high, I-20 visible sign to the roof of the store to the roof of the pump carport and back again. You never realize how many there are until they all take wing at the same time in Hitchcockian fashion.
I'm not sure why an exit gas station off a high traffic Interstate would go under, but I will note that the exit from I-20 to Wilson is a bit odd in that you come out on the other side of the street than you expect, and would then have to make a left to get to Gaz-Bah, while there is a travel plaza directly in front of you that requires no turn.