The Appalachian Mountains are considered to be 500 million years old.

The formation of the Appalachian Mountains began during the Ordovician Period, around 480 million years ago, with significant geological activity occurring over hundreds of millions of years. The mountains have undergone various processes, including tectonic uplift, erosion, and glaciation, contributing to their current shape and structure. This long geological history makes the Appalachians one of the oldest mountain ranges in North America, reflecting a rich and complex past that has shaped the landscape and ecosystems of the region.