The Rocky Mountains were formed from 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began to slide underneath the North American plate. The angle of subduction was shallow, resulting in a broad belt of mountains running down western North America. Since then, erosion by water and glaciers have sculpted the Rockies into dramatic peaks and valleys. At the end of the last ice age, humans started to inhabit the mountain range. After Europeans, such as Sir Alexander MacKenzie and the Lewis and Clark expedition, started to explore the range, minerals and furs drove the initial economic exploitation of the mountains, although the range itself never became densely populated.
A road is a thoroughfare, route, or way on land between two places, which has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways (British English: carriageways) each with one or more lanes and also any associated sidewalks (British English: pavement) and road verges. Roads that are available for use by the public may be referred to as public roads or highways.