Sierra Madre Oriental
The Sierra Madre Oriental is part of the American Cordillera.  The American Cordillera is a row of mountains that go from North America to Antarctica. is about 700 miles long (1000 kilometers).  They are about 60 million years old.  They are made of limestone rock and shale rock.  They have copper, iron, and other important metals in them.  The tallest mountain in the Sierra Madre Oriental is about 12,000 feet high (3600 meters).  The Rio Grande is the space between the Rocky Mountains and the Sierra Madre Oriental Mountains.