Are the posters the only method you have used to try to find the owner? Have you checked with your Animal Control office to see if they have had any calls from someone missing a dog of this discription. How about letting the local Shelters know that you have found this animal. If I had lost a dog, that would be one place I would call. Also local newpapers generally have a lost and found section which people can advertise if they have lost a pet. What about contacting the people that put on the fair? Other than that, if you feel you have exhausted all reasonable means to find the owner, I'd would say keep the dog. You want a dog, this one needs a home, you obviously know a quite a bit about her at this point and you like her and she likes you. I think the question already has an answer. KEEP THE DOG.