On the West End of Pittsburgh there is a place called the Old Stone Tavern, which has a cornerstone that reads 1752.
That would have dated it to when the French were running the place.
There is some debate as to whether that date is accurate, though there is documentation of the Old Stone up and running in the 1790’s. Unfortunately it would not make this list as the most recent owners closed-up eight or nine years ago.
Cornerstone only says when it was built, or laid. Does not mean it was a restaurant. Indeed, one of the old places listed here states it was a hotel before a restaurant, but the date is for the latter only.