The Sierra la Mariquita is a Sky Island mountain in northern Sonora owned by the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), the Mexican national astronomy agency. The Observatorio Astrofísico Guillermo Haro was built on the summit in 1987. It is located northwest of the copper mining town of Cananea, only 26 km south of the Arizona border. The Sierras la Mariquita and Elenita form a high elevation Sky Island complex connected by oak woodland in Puerto Cananea, north and south of Mexico Federal Highway 2. They are sister ranges to the Huachuca Mountains of Arizona.