Sea of river rock

I'm honestly not sure whether the large flat-roofed section along the left side of the store is original or a later addition. It certainly looks tacked-on, but it's really hard to tell from historic aerials, and surely this sort of river rock would have gone out of fashion by the time of any addition (unless it was really early). Anyway, it's a little unusual seeing this much river rock on a Safeway, but I suspect it was added to appease suburbanites concerned about aesthetics since on a typical Safeway from this era, this would be all plain concrete blocks.