Final answer:
The Appalachian mountain range was created approximately 300 million years ago through multiple collisions and tectonic events during the Paleozoic era.
Step-by-step explanation:
The Appalachian mountain range was probably created during the Paleozoic era through multiple collisions with small island chains and eventually with the supercontinent of Gondwana during the formation of Pangaea.
The mountains were formed over a span of about 220 million years, with three major tectonic events known as the Taconic, Acadian, and Alleghenian orogenies.
Based on this information, the Appalachian mountain range was most likely created approximately 300 million years ago.