San Antonio Mountain, Volcanic summit in Rio Arriba County, New Mexico, US.

San Antonio Mountain is a free-standing dacite dome in Rio Arriba County, New Mexico, reaching 10,908 feet, the highest peak in the Taos Plateau volcanic field. It rises from sagebrush plains of the lower San Luis Valley, measures five miles across its base, and has north and south summits separated by a shallow saddle.

San Antonio Mountain is a dacite dome built from lava flows up to 30 meters thick that erupted between 3.36 and 2.9 million years ago. The flows are glassy at their bases, grey and massive in the middle, and blocky on top, sometimes oxidized red. A shallow saddle separates the north and south summits, and cinder and spatter around the southern summit mark the youngest vent. The dome almost buries an older andesite cone to the northwest.

The Tewa people of the Rio Grande valley call this peak Bear Mountain and regard it as a sacred location connected to the north direction in their traditional beliefs. It serves as an important marker in their understanding of the landscape.

Forest Road 418 provides the main approach to the summit, though visitors must navigate around private property boundaries and hike the final stretch through Carson National Forest. Plan for rough terrain and minimal facilities at the mountain.

San Antonio Mountain is the highest peak of the Taos Plateau volcanic field, yet it is shorter than Grouse Mesa and Wheeler Peak in the surrounding ranges. Because it stands alone, it can be seen from 60 or more miles away in southern Colorado and northern New Mexico.