section_path: Geography
section_name: Geography
paragraph_text: Geography
  
  The Rocky Mountains are the easternmost portion of the expansive North American Cordillera. They are often defined as stretching from the Liard River in British Columbia south to the headwaters of the Pecos River, a tributary of the Rio Grande, in New Mexico. The Rockies vary in width from 110 to 480 kilometres (70 to 300 miles). The Rocky Mountains contain the highest peaks in central North America. The range's highest peak is Mount Elbert in Colorado at 4,401 metres (14,440 feet) above sea level. Mount Robson in British Columbia, at 3,954 m (12,972 ft), is the highest peak in the Canadian Rockies.
  
  The eastern edge of the Rockies rises dramatically above the Interior Plains of central North America, including the Sangre de Cristo Mountains of New Mexico and Colorado, the Front Range of Colorado, the Wind River Range and Big Horn Mountains of Wyoming, the Absaroka - Beartooth ranges and Rocky Mountain Front of Montana and the Clark Range of Alberta.
  
  Central ranges of the Rockies include the La Sal Range along the Utah -Colorado border, the Abajo Mountains and Henry Mountains of Southeastern Utah, the Uinta Range of Utah and Wyoming, and the Teton Range of Wyoming and Idaho.
  
  The western edge of the Rockies includes ranges such as the Wasatch near Salt Lake City, the San Juan Mountains of New Mexico and Colorado, the Bitterroots along the Idaho-Montana border, and the Sawtooths in central Idaho. The Great Basin and Columbia River Plateau separate these subranges from distinct ranges further to the west. In Canada, the western edge of the Rockies is formed by the huge Rocky Mountain Trench, which runs the length of British Columbia from its beginning as the Kechika Valley on the south bank of the Liard River, to the middle Lake Koocanusa valley in northwestern Montana.
  
  The Canadian Rockies are defined by Canadian geographers as everything south of the Liard River and east of the Rocky Mountain Trench, and do not extend into Yukon, Northwest Territories or central British Columbia. They are divided into three main groups: the Muskwa Ranges, Hart Ranges (collectively called the Northern Rockies) and Continental Ranges. Other more northerly mountain ranges of the eastern Canadian Cordillera continue beyond the Liard River valley, including the Selwyn, Mackenzie and Richardson Mountains in Yukon as well as the British Mountains / Brooks Range in Alaska, but those are not officially recognized as part of the Rockies by the Geological Survey of Canada, although the Geological Society of America definition does consider them parts of the Rocky Mountains system as the "Arctic Rockies".
  
  The Continental Divide of the Americas is in the Rocky Mountains and designates the line at which waters flow either to the Atlantic or Pacific Oceans. Triple Divide Peak (2,440 m or 8,020 ft) in Glacier National Park is so named because water falling on the mountain reaches not only the Atlantic and Pacific but Hudson Bay as well. Farther north in Alberta, the Athabasca and other rivers feed the basin of the Mackenzie River, which has its outlet on the Beaufort Sea of the Arctic Ocean.
  
  Human population is not very dense in the Rockies, with an average of four people per square kilometer and few cities with over 50,000 people. However, the human population grew rapidly in the Rocky Mountain states between 1950 and 1990. The forty-year statewide increases in population range from 35% in Montana to about 150% in Utah and Colorado. The populations of several mountain towns and communities have doubled in the forty years 1972–2012. Jackson, Wyoming, increased 260%, from 1,244 to 4,472 residents, in those forty years.