Because North America and Africa were once geographically connected, the Appalachians formed part of the same mountain chain as the Little Atlas in Morocco. This mountain range, known as the Central Pangean Mountains, extended into Scotland, before the Mesozoic Era opening of the Iapetus Ocean, from the North America/Europe collision (See Caledonian orogeny)

By the end of the Mesozoic Era, the Appalachian Mountains had been eroded to an almost flat plain.[27] It was not until the region was uplifted during the Cenozoic Era that the distinctive topography of the present formed.