Piedras Negras is a city in the Coahuila state of Mexico, located at 28.71°N,100.53°W. It borders on the town of Eagle Pass, Texas across the Rio Grande or Rio Bravo. Before the Mexican Revolution, Piedras Negras was known as Ciudad Porfirio Diaz. In 2003 Piedras Negras had an estimated population of 132,900 people.
