The Plains of San Agustin (sometimes listed as the Plains of San Augustin) is a region in the southwestern U.S. state of New Mexico in the San Agustin Basin, south of U.S. Highway 60. The area spans Catron and Socorro Counties, about 50 miles (80 km) west of the town of Socorro and about 25 miles (40 km) north of Reserve. The plains extend roughly northeast-southwest, with a length of about 55 miles (88 km) and a width varying between 5–15 miles (8–24 km). The basin is bounded on the south by the Luera Mountains and Pelona Mountain (outliers of the Black Range); on the west by the Tularosa Mountains; on the north by the Mangas, Crosby, Datil, and Gallinas Mountains; and on the east by the San Mateo Mountains. The Continental Divide lies close to much of the southern and western boundaries of the plains.[1]