Appalachian Mountains

The Appalachian Mountains, sometimes known as the Appalachians, are a mountain range in eastern to northern North America. During the Ordovician Period, the Appalachians initially developed some 480 million years ago. They formerly reached altitudes comparable to the Alps and the Rocky Mountains before succumbing to natural erosion. The Appalachian Mountains are a barrier to east–west movement because they form a sequence of alternating ridgelines and valleys that are angled in opposition to most routes and trains that go east–west.