Excavations at the site have dated construction of a "causewayed camp" back to around 3000 BCE. An extensive bank and ditch as well as burial mounds are evident from this period. However most of the works at the site date from around 450 to 300 BCE, when existing works were extended and enlarged with three new ditch-and-bank earthworks built creating the main fortifications in a set of three concentric rings with offset entrance points.
The fort was occupied by the Durotriges tribe at the time of the Roman invasion. It was attacked and invested by the 2nd legion under Vespasian in 43 CE. The Romans occupied the site but concentrated their efforts in the area around Durnovaria. There was some Roman construction at the site, including a small temple built around 400 CE. The site was abandoned by the Romans soon after that date and was not re-occupied, remaining deserted from then on.
The name Maiden is believed to derive from the Celtic for great hill, mai dun.