I found these a week ago at my farm when I took my little boy to our pond fishing. I have grown up hunting in the Appalachian mountains here and have hunted every known animal here. I do not know what left these. All the tracks were very crisp and clear. No slippage or slide marks in the mud on a slope which tells me it was most likely moving at a walking pace. I made some reference marks that I could measure once I got home. The tracks measured 4" x 4" and the stride measured a varied 35"-40". I measured the stride in 3 places. The tracks were definitely canine. 100% sure of that.
When I was a teenager I was stalked through the woods all the way to my uncles back door by a large jet black canine. One big enough to have made tracks this size but I have never seen anything like it since then. Until I found these tracks. Not that I'm implying they are connected. BTW that experience as a teenager gave me horrific nightmares for well over a decade before I finally conquered them.
I took 2 pictures. One with my wife's boot, one with my wallet. I crudely drew a line on the wallet pic to help your orient the track. You can then clearly see the track in the unlined pic. Claw marks and all.