The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. The physiography of the province is the result of tectonic extension that began around 17 million years ago in the early Miocene epoch.
The Basin and Range Province includes much of western North America. In the United States, it is bordered on the west by the eastern fault scarp of the Sierra Nevada and spans over 500 miles (800 km) to its eastern border marked by the Wasatch Fault, the Colorado Plateau and the Rio Grande Rift. The province extends north to the Columbia Plateau and south as far as the Trans-Mexican Volcanic Belt in Mexico, though the southern boundaries of the Basin and Range are debated. In Mexico, the Basin and Range Province is dominated by and largely synonymous with the Mexican Plateau.
Clarence Dutton famously compared the many narrow parallel mountain ranges that distinguish the unique topography of the Basin and Range to an “army of caterpillars marching toward Mexico.”
The Basin and Range Province should not be confused with The Great Basin, which is a sub-section of the greater Basin and Range physiographic region defined by its unique hydrological characteristics (internal drainage).