Transmountain Road is a part of Loop 375 which connects Northeast El Paso

Northeast El Paso

Northeast El Paso is part of the city of El Paso, Texas and is located North of Central El Paso, and East of the Franklin Mountains. Development of the area started during the 1950s, when many homes were demolished in the process of the construction of Interstate 10...

 to West El Paso between Patriot Freeway (U.S. Highway 54) and Interstate 10. It crosses through the Franklin Mountains

Franklin Mountains (Texas)

The Franklin Mountains of Texas are a small range that extend from El Paso, Texas north into New Mexico. The Franklins were formed due to crustal extension related to the Cenozoic Rio Grande rift...

 with its highest elevation (5280 ft) at the crest of Smuggler's Pass. It was officially opened August 5, 1969, and considered to be the largest excavation project in Texas History. It carries that distinction to this day.

Geology

Transmountain Road has many roadcuts which expose outcrops of Precambrian

Precambrian

The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...

rocks, which are some of the oldest in Texas. Units exposed include:

• Red Bluff Granite
• Castner Marble
• Mundy Breccia
• Lanoria Formation
• Thunderbird Group (large roadcut at Smuggler's Pass)