The mountains on the horizon mark the start of the Jornada del Muerto, a feared section of El Camino Real de Tierra Adentro that forced travelers to cross 90 miles of open desert. Travelers had followed the Rio Grande to this point because the river provided water and a gentle path, but south of here the river valley grew too rough for loaded carros and carretas to pass through, forcing caravans to risk a desert crossing. The open lands offered few water sources and no protection from raiding parties, so southbound groups began crossing at night in hopes that summer storms had refilled water sources. For northbound travelers, seeing these mountains meant they had survived the crossing. The trail passed Mesa del Contadero, also known as Black Mesa or Mesa de Senecú, where Spanish caravans placed a person on top to count livestock entering the Jornada and survivors leaving it. At the base of Fra Cristóbal Mountain, caravans built a paraje that served as the last chance to find water and graze livestock before starting the Jornada del Muerto.