The Franklin Mountains of Texas (previously known as Las Sierras de los Mansos[1]) are a small range (23 miles long, 3 miles (4.8 km) wide) that extend from El Paso, Texas north into New Mexico.[2] The Franklins were formed due to crustal extension related to the Cenozoic Rio Grande rift. Although the present topography of the range and adjoining basins is controlled by extension during rifting in the last 10 million years, faults within the range also record deformation during the Laramide orogeny, between 85 and 45 million years ago.