Castner Range National Monument is a national monument in El Paso County, Texas, United States that covers 6,672 acres (27 km2) of the Franklin Mountains. It was established by President Joe Biden on March 21, 2023. The monument, a former weapons testing range, is part of Fort Bliss and is managed by the U.S. Army as the only land conservation national monument within the Department of Defense. The monument includes the eastern slopes of North Franklin Mountain, the highest peak in the area. It is adjacent to Franklin Mountains State Park and Northeast El Paso and near the Organ Mountains–Desert Peaks National Monument in New Mexico. As remediation is ongoing, the site is closed to the public.