A Roman fort (""), Mamucium or Mancunium was established in what is now Castlefield around AD 79 near a crossing place on the River Medlock. The fort was sited on a sandstone bluff near the confluence of the River Medlock and Irwell in a naturally defensible position. It was erected as a series of fortifications established by Gnaeus Julius Agricola during his campaign against the Brigantes, who were the Celtic tribe in control of most of northern England. It guarded a central stage of the Roman road (equivalent to Watling Street), between Deva Victrix (Chester) and Eboracum (York). Another road branched off to the north to Bremetennacum (Ribchester). The neighbouring forts were Castleshaw and Northwich. Built first from turf and timber, the fort was demolished around 140. When it was rebuilt around 160, it was again of turf and timber construction. Around the year 200, the fort underwent another rebuild enhancing its defences by replacing the gatehouse in stone and facing the walls with stone. The fort would have been garrisoned by an infantry cohort of around 500 auxiliary troops.