Liard River in the context of "Canadian Cordillera"

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 (4,800 km) in a straight-line distance from the northernmost part of Western Canada, to New Mexico in the Southwestern United States. Depending on differing definitions between Canada and the U.S., its northern terminus is located either in northern British Columbia's Terminal Range south of the Liard River and east of the Trench, or in the northeastern foothills of the Brooks Range/British Mountains that face the Beaufort Sea coasts between the Canning River and the Firth River across the Alaska–Yukon border. Its southernmost point is near the Albuquerque metropolitan area, adjacent to the Rio Grande rift, and north of the Sandia–Manzano Mountain Range, also near Santa Fe, New Mexico. Being the easternmost portion of the North American Cordillera, the Rockies are distinct from the tectonically younger Cascade Range and Sierra Nevada, which both lie farther to its west.

The Rockies formed 55 million to 80 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. After explorations of the range by Europeans, such as Sir Alexander Mackenzie, and Anglo-Americans, such as the Lewis and Clark Expedition, natural resources such as minerals and fur drove the initial economic exploitation of the mountains, although the range itself has never experienced a dense population.

The Canadian Rockies (French: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part of the Canadian Cordillera, which is the northern segment of the North American Cordillera, the expansive system of interconnected mountain ranges between the Interior Plains and the Pacific Coast, that runs northwest–southeast from central Alaska to the Isthmus of Tehuantepec in Mexico.

Canada officially defines the Rocky Mountains system as the mountain chains east of the Rocky Mountain Trench extending from the Liard River valley in northern British Columbia to the Albuquerque Basin in New Mexico, not including the Mackenzie, Richardson and British Mountains/Brooks Range in Yukon and Alaska (which are all included as the "Arctic Rockies" in the United States' definition of the Rocky Mountains system). The Canadian Rockies, being the northern segment of this chain, is thus defined as comprising the central-eastern section of the North American Cordillera, between the Prairies of Alberta and the Liard Plain of northeastern British Columbia to the east and the Interior Mountains/Plateau and Columbia Mountains to the west. It is divided into the Northern Rockies (which is further subdivided into the Muskwa and Hart Ranges) and Continental Ranges, separated by the McGregor River valley, the McGregor Pass and the Kakwa River valley.

The Rocky Mountain Foothills are an upland area flanking the eastern side of the Rocky Mountains, extending from the Liard River in British Columbia southward into Alberta. Bordering the Interior Plains system, they are part of the Rocky Mountain System or Eastern System of the Western Cordillera of North America.

The Terminal Range is the northernmost mountain range of the Canadian Rockies, so-named for its position at the northern terminus of the Rockies. Lying west of Muncho Lake and the Trout River, its northern perimeter is the Liard River. The Sentinel Range lies to its east.

The Rocky Mountain Trench, also known as the Valley of a Thousand Peaks or simply the Trench, is a large valley on the western side of the northern part of North America's Rocky Mountains. The Trench is both visually and cartographically a striking physiographic feature extending approximately 1,600 km (1,000 mi) from Flathead Lake, Montana, to the Liard River, just south of the British Columbia–Yukon border near Watson Lake, Yukon. The trench bottom is 3–16 km (1.9–9.9 mi) wide and is 600–900 m (2,000–3,000 ft) above sea level. The general orientation of the Trench is an almost straight 150/330° geographic north vector and has become convenient as a visual guide for aviators heading north or south.

Although some of its topography has been carved into U-shaped glacial valleys, it is primarily a byproduct of geologic faulting. The Trench separates the Rocky Mountains on its east from the Columbia Mountains and the Cassiar Mountains on its west. It also skirts part of the McGregor Plateau area of the Nechako Plateau sub-area of the Interior Plateau of British Columbia. It is up to 25 km (16 mi) wide, if measured peak-to-peak, and varies in valley relief, but is clearly visible by air and satellite/remote sensing and is easily discernible to those ascending any of the mountains or ridges lining it.

The Brooks Range (Gwich'in: Gwazhał) is a mountain range in far northern North America stretching some 700 miles (1,100 km) from west to east across northern Alaska into Canada's Yukon Territory. Reaching a peak elevation of 8,976 feet (2,736 m) on Mount Isto, the range is believed to be approximately 126 million years old.

In the United States, these mountains are considered a subrange of the Rocky Mountains, whereas in Canada they are considered separate, as the northern border of the Rocky Mountains is considered to be the Liard River far to the south in the province of British Columbia.