Trap Mountain is a 4,122-foot summit in the Chisos Mountains of far West Texas within Big Bend National Park, rising steeply from the surrounding Chihuahuan Desert above Ross Maxwell Scenic Drive. Formed chiefly of Burro Mesa Rhyolite about 29 million years ago, it is marked by dark volcanic outcrops on its west slope that help explain its name, taken from trap rock. The name has appeared in published use since at least 1914 and was officially adopted by the United States Board on Geographic Names. In its hot arid climate, the mountain supports desert plants such as creosote bush, ocotillo, lechuguilla, and yucca, with sparse runoff draining toward the Rio Grande.