Sierra Madre Occidental 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. The Sierra Madre is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica. The Spanish name "sierra madre" means "mother mountains" and "occidental" means "western" in English, with these being the "Western Mother Mountains". To the east, from the Spanish "oriental" meaning
Arizona/New Mexico Mountains ecoregion other outlier ranges considered part of the Arizona/New Mexico Mountains ecosystem. Arizona/New Mexico Mountains ecoregion The Arizona/New Mexico Mountains ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) in the U.S. states of Arizona and New Mexico. The region is a transition region from the lower elevation Sonoran Desert (81) to the southwest and Chihuahuan Desert (24) southeast; the west is bordered by the mid elevation Mojave Desert (14). The north is bordered by the east-west "Arizona/New Mexico Plateau" (22), ecoregion which is part of and is the southern region of the Colorado Plateau.