Sierra San Antonio
The Sierra San Antonio is a mountain range in southernmost Arizona state (U.S.) and northern Sonora state (México). Geography. The approximately long range is the southern section of the Patagonia Mountains, beginning in the U.S.-Mexico border area, and descending to lower elevations in México. The range is named after the Roman Catholic Saint Antonio. The Sierra La Esmeralda, northernmost range of the Sierra Madre Occidental cordillera, begins south of the Sierra San Antonio. Two miles (3.2 km) north of the border and the Sierra San Antonio is Mount Washington at 7,221 ft (2,201 m), the highest peak  of the Patagonia Mountains. Regional sky island ecology. Various species are studied in the Madrean Sky Islands habitats in higher elevation mountains of northern Sonora and Chihuahua, southeast Arizona, and southwestern New Mexico. One example is research on horned lizards in mountainous areas in northern Mexico in various mountain ranges, including the Sierra San Luis range to the east.