In Diocletian's great reform of the administrative system of the empire, the whole of Roman Africa, with the exception of Mauretania Tingitana (which was attached to the province of Spain), constituted a single diocese subdivided into six provinces: Zeugitana (Carthage), Byzacium (Hadrumetum, now Susa), Numidia Cirtensis (Cirta, Constantine), Tripolitana (Tripolis), Mauretania Sitifensis (Sitifis, Setif), and Mauretania Caesariensis (Caesarea, now Cherchel).
Apart from the province of Constantine, Algeria is less rich in Roman remains than Tunisia; mention must, however, be made of the excavations of Victor Waille at Cherchel, where were found fine statues in the Greek style of the time of King Juba II.; of P. Gavault at Tigzirt (Rusuccuru), and finally of those of Stephane Gsell at Tipasa (basilica of St Salsa) and throughout the district of Setif and at Khamissa (Thuburticum Numidarum).
Setif (12,261), the Sitifis Colonia of the Romans, is 50 m.
Phosphate beds are also worked near Setif, Guelma and Ain Beida.
Marshal Sylvain Charles Valee (1773-1846), who replaced him, founded Philippeville to serve as a seaport for the region of Constantine, occupied Jijelli, and at the head of the expeditionary column returned from Constantine to Algiers by the interior, passing through Setif and les Portes de fer.
Neither the Romans nor the Turks had been able to subdue this square mountainous tract, of which Bougie, Setif, Aumale and Dellys form the four corners.