3 March 1947 | Erected | Archdiocese of La Plata (Colón, Pergamino, San Nicolás de los Arroyos, Ramallo, Bdrtolomé Miter, San Pedro, Baradero, San Antonio de Areco, Exaltación de la Cruz, General Tlriburu, and Campa)
Diocese of Mercedes (Rojas and Marcelino Ugarte)
| Diocese of San Nicolás de los Arroyos (erected)
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