Bones evolved for the first time: "485 Ma First vertebrates with true bones (jawless fishes)" -- https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life (Vertebrates existed without a bony notochord before then.)

But the Appalachians were started much earlier: "The geologic processes that led to the formation of the Appalachian Mountains started 1.1 billion years ago." They were basically finished growing by the time bones existed: "Around 480 million years ago, geologic processes began that led to three distinct orogenic eras that created much of the surface structure seen in today's Appalachians. [d] During this period, mountains once reached elevations similar to those of the Alps and the Rockies" Since then, it's just been wearing down. -- https://en.wikipedia.org/wiki/Appalachian_Mountains