Thank you for the information! This is a possible match. My gfather was supposed to be educated, so I am surprised at his spelling, but can find no other explanation since no one has ever heard of Greanoke, PA. (I would assume it to be pronounced like Roanoke, VA) I will have to find out if Green Oak has records going back to 1875 and track it down from there.
Again, thank you so much for the information. This may well be a piece of the puzzle.