Hot answers tagged united-states
It looks like a Burl. They are natural non-harmful (think of them like scar tissue maybe, resulting from injury or infection) deformities in the grain of trees. Both hardwood & softwood trees can develop burls. (FWIW, I'd guess based on the bark & needles laying in the folds of the bark in the first picture that this tree is some sort of conifer.)
This is impossible to answer unless you are willing to do a enormous amount of research. There is no single, or even just a few, databases of trails in the US. The national trail lists generally only contain the larger multi-state trails (like the AT, PCT, etc) and some of the larger regional trails, but these are the tip of the iceberg. I'm guessing, but ...
I was pleased to see the photos of the burls; it's been some time since I had thought of all of the splendid uses Native Americans and others had found for burls, so I hope no-one minds my digression. Burls are caused by wounds to trees, as has been mentioned. But far from making the tree unattractive, burls had been valued! They had been sought out by ...
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