The Appalachian Mountains are estimated to be around 500 million years old.

This age reflects their formation during several geological events, including the collision of tectonic plates and the processes of erosion and uplift over millions of years. The mountains have undergone significant changes throughout their history, leading to their current rolling hills and ridges. Their ancient origins contribute to the unique geology, biodiversity, and ecosystems found in the region today, making the Appalachians a significant natural feature of North America.