The ruins were left undisturbed until Manchester expanded rapidly during the Industrial Revolution in the late 18th century. Most of the fort was levelled to make way for new developments such as the construction of the Rochdale Canal and the Great Northern Railway. The site is now part of the Castlefield Urban Heritage Park that includes renovated warehouses. A section of the fort's wall along with its gatehouse, granaries, and other ancillary buildings from the vicus have been reconstructed and are open to the public.
Mamucium is generally thought to represent a Latinisation of an original Brittonic name, either from mamm- ("breast", in reference to a "breast-like hill") or from mamma ("mother", in reference to a local river goddess). Both meanings are preserved in languages derived from Common Brittonic, mam meaning "breast" in Irish and "mother" in Welsh. The neuter suffix -ium is used in Latin placenames, particularly those representing Common Brittonic -ion (a genitive suffix denoting "place or city of ~"). The Welsh name for Manchester is Manceinion and presumably derives from the original Brittonic form.
The Romans built the fort on a naturally defensible sandstone bluff that overlooked a nearby crossing over the River Medlock. The area became an important junction for at least two major military roads through this part of the country. One highway ran east to west between the legionary fortresses of Deva Victrix (Chester) and Eboracum (York) the other ran north to Bremetennacum (Ribchester). In addition, Mamucium may also have overlooked a lesser road running north west to Coccium (Wigan). The fort was one of a chain of fortifications along the Eboracum to Deva Victrix road, with Castleshaw Roman fort lying 16 miles (26 km) to the east, and Condate (Northwich) 18 miles (29 km) to the west. Stamps on tegulae indicate that Mamucium had administrative links not only with Castleshaw, but also with Ardotalia, the nearest fort (12 miles), Slack and Ebchester; all the forts probably got the tegulae from the same place in Grimescar Wood near Huddersfield.
There is no evidence that a prehistoric settlement occupied the site before the arrival of the Romans. However, Stone Age activity has been recorded in the area. Two Mesolithic flints and a flint flake as well as a Neolithic scraper have been discovered. A shard of late Bronze Age pottery has also been found in situ. Although the area was in the territory of the Celtic tribe Brigantes, it may have been under the control of the Setantii, a sub-tribe of the Brigantes, when the Romans took control from the ancient Britons.
Construction of Mamucium started around AD 79 during the campaigns of General Julius Agricola against the Brigantes after a treaty failed. Excavations show the fort had three main phases of construction: first AD 79, second around AD 160, and third in AD 200.