Organ Mountains

Organ Mountains
The Organ Mountains seen from the west
Dimensions
Length	85 mi (137 km) N-S
Width	42 mi (68 km) W-E
Geography
Location of the Organ Mountains within New Mexico
Country	United States
State	New Mexico
Region	(northwest)-Chihuahuan Desert
District	Doña Ana County, NM
Range coordinates	32°20′N 106°34′W / 32.33°N 106.56°W / 32.33; -106.56Coordinates: 32°20′N 106°34′W / 32.33°N 106.56°W / 32.33; -106.56
Borders on	San Andres Mountains
Geology
Type of rock	granite, rhyolite

The Organ Mountains are a rugged mountain range in southern New Mexico in the Southwestern United States. Organ Mountains-Desert Peaks National Monument was declared a national monument on May 21, 2014. They lie 10 miles (16 km) east of the city of Las Cruces, in Doña Ana County.

The Organ Mountains are near the southern end of a long line of mountains on the east side of the Rio Grande's rift valley. The range is nearly contiguous with the San Andres Mountains to the north and the Franklin Mountains to the south, but is very different geologically. Whereas the San Andres and Franklin Mountains are both formed from west-dipping fault blocks of mostly sedimentary strata (with limestone most prominent), the Organ Mountains are made primarily of igneous rock (intrusive granite and extrusive rhyolite). Their name reflects their similarity in appearance (particularly the granite "needles" in the highest part of the range) with pipes that would be part of a pipe organ.

The San Andres Mountains-(southern subrange of San Augustin Mountains), are separated from the Organ Mountains by San Augustin Pass, through which U.S. Highway 70 passes on its way to White Sands Missile Range, White Sands National Monument and Alamogordo. The Franklin Mountains are separated from the Organ Mountains by a 10-mile wide low area known as Anthony Gap. Much of this intervening land is part of Fort Bliss.