Six of the nine Brigantian poleis described by Claudius Ptolemaeus in the Geographia fall within the historic county.
Their capital was at Petuaria, close to the Humber estuary.
Another emperor, Constantius Chlorus, died in Yorkshire during a visit in 306 AD.
This saw his son Constantine the Great proclaimed emperor in the city, who would become renowned due to his contributions to Christianity.
The Brigantes controlled territory which later became all of the North Riding of Yorkshire and the West Riding of Yorkshire.
The Kingdom of Wessex was now in its ascendant and established its dominance over the North in general, placing Yorkshire again within Northumbria, which retained a certain amount of autonomy as an almost-independent earldom rather than a separate kingdom.
The Wessex Kings of England were reputed to have respected the Norse customs in Yorkshire and left law-making in the hands of the local aristocracy.
Although the Roman conquest of Britain began in 43 AD, the Brigantes remained in control of their kingdom as a client state of Rome for an extended period, reigned over by the Brigantian monarchs Cartimandua and her husband Venutius.
Initially, this situation suited both the Romans and the Brigantes, who were known as the most militant tribe in Britain.