Chihuahua ([tʃiˈwawa]) is a state in north western Mexico with a mainland area of 247,087 square kilometers (95,400.8 sq mi), slightly larger than the United Kingdom. It is surrounded by the states of Sonora to the west, Sinaloa to the south-west, Durango to the south, and Coahuila to the east, and by the U.S. states of Texas to the north-east and New Mexico to the north. Chihuahua is the largest state in Mexico by area, and is consequently known under the nickname El Estado Grande ("The Big State"). Although Chihuahua is primarily identified the Chihuahuan Desert for namesake, it has more forests than any other state in Mexico. Due to its variant climate the state boasts a large variety of fauna and flora. The state is mostly characterized by rugged mountainous terrain and wide river valleys. The Sierrra Madre Occidental mountain range, an extension of the Rocky Mountains, dominates the state's terrain and is home to the state's greatest attraction, La Barranca del Cobre, or Copper Canyon, a spectacular canyon system larger and deeper than the Grand Canyon. On the slope of the Sierra Madre Occidental mountains (around the regions of Casas Grandes, Cuauhtémoc and Parral), there are vast prairies of short yellow grass, the source of the bulk of the state's agricultural production. Most of the 3.2 million inhabitants (2005) live along the Rio Grande Valley and the Conchos River Valley.