Piedras Negras is the name of a city as well as the name of its surrounding municipality in the Mexican state of Coahuila. It stands at the northeastern edge of Coahuila on the U.S.-Mexico border, across the Río Bravo (Rio Grande) from Eagle Pass in the U.S. state of Texas. The city was founded in 1849. It was renamed Ciudad Porfirio Díaz in 1888, in homage to President Porfirio Díaz, but reverted to its original name following the Mexican Revolution. In Spanish Piedras Negras translates to "black rocks" – a reference to the coal deposits that exist in the area. Across the river, coal was formerly mined on the US side at Dolchburg, near Eagle Pass. This mine closed around 1905, after a fire. Mexico currently operates two large coal-fired power plants named "José López Portillo" and "Carbón 2" located 30 miles (48 km) south of Piedras Negras.