The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch 3,000 mi in straight-line distance from the northernmost part of British Columbia, in western Canada, to New Mexico in the Southwestern United States. The northern terminus is located in the Liard River area east of the Pacific Coast Ranges, while the southernmost point is near the Albuquerque area adjacent the Rio Grande Basin and north of the Sandia–Manzano Mountain Range. Located within the North American Cordillera, the Rockies are distinct from the tectonically younger Cascade Range and Sierra Nevada, which both lie farther to the west.
The Rocky Mountains formed 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began sliding 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, further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks and valleys. At the end of the last ice age, humans began inhabiting the mountain range.