Basin and Range Province, Physiographic province in the Western United States and northwestern Mexico

The Basin and Range Province is a physiographic province of roughly 3,000 km by up to 1,000 km, spanning parts of Arizona, California, Idaho, New Mexico, Oregon, Texas, Utah and nearly all of Nevada, plus Baja California, Sonora and Chihuahua in Mexico. Its topography alternates north-south faulted mountain ranges with flat basins, a horst-and-graben pattern formed by crustal extension. Clarence Dutton likened the parallel ranges to an "army of caterpillars crawling northward."

Around 17 million years ago during the early Miocene, the crust in this zone began to stretch and thin through tectonic extension. Over millions of years these processes created the mountain ranges that rose from the plain while basins sank.

The province's name comes from its alternating basins and ranges, a term geologists use for the horst-and-graben structure formed by crustal extension. Clarence Dutton described the parallel ranges as an "army of caterpillars crawling northward." The province overlaps the Great Basin but is not the same thing: the Great Basin is defined by internal drainage, while Basin and Range is a physiographic and tectonic unit.

The province spans parts of Arizona, California, Idaho, Nevada, New Mexico, Oregon, Texas and Utah, plus Baja California, Sonora and Chihuahua in Mexico. Its north-south ranges force most roads to cross passes; the Wasatch Fault, Colorado Plateau and Rio Grande Rift mark the eastern edge. The Sierra Madre Occidental splits the Mexican portion in two.

The terrain displays a repeating pattern of parallel mountain ranges rising roughly 3000 to 5000 feet (900 to 1500 meters) above valley floors. Death Valley marks the lowest point in the entire province, lying far below sea level.