Ciudad Porfirio Díaz
Ciudad Porfirio Díaz,Mexico: see Piedras NegrasPiedras Negras,
city (1990 pop. 96,178), Coahuila state, N Mexico, on the Rio Grande opposite Eagle Pass, Tex. Founded in 1849, the city grew as an international shipping point. Piedras Negras is a commercial and processsing center for the surrounding agricultural region.
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