The Sierra Madre del Sur range and the Sierra Madre Occidental. The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through Northwestern and Western Mexico, and along the Gulf of California. <span>The Sierra Madre del Sur joins with the </span>Eje Volcánico Transversal<span> (Trans-Mexican Volcanic Belt) of central Mexico in northern Oaxaca. Sites: wiki </span>
