The Roman fort, Mamucium, on the sandstone bluff at the junction of the Rivers Irwell and Medlock gave Castlefield its name. The fort's remains including a short, seven feet high section of wall are protected as a scheduled monument. The Romans left Mamucium in 410 AD and the settlement was subsequently occupied by Saxons who renamed it "Manigcastre". It was taken by the Danes in 870 AD, the significance of which is seen in the street patterns and names. The "gate" suffix in Deansgate and Millgate derives from the Old Norse "gata" meaning road. In the tenth century the cliff at the junction of the Irwell and the Irk became the preferred site when a church dedicated to St Mary was built at St Mary's Gate and the Danish town grew around it. The settlement was important enough to be given the right to strike coinage by King Canute.