Northumbria was formed in the early7th century byAthelfrith, King ofBernicia.[1] He conquered the kingdom ofDeira and severalBritish kingdoms and combined them under his rule.[2] The kingdom of Northumbria also includedLindsey at times. Northumbria was a part of theHeptarchy ofAnglo-Saxon kingdoms.[3] At its greatest the kingdom extended at least from just south of the Humber river, to theRiver Mersey and to theForth (roughly,Sheffield toRuncorn toEdinburgh). The name 'Northumbria' wasn't in common use until the time of Ecgfrith, King of Northumbria.[1] The name is first used in thepreamble to the council of Hatfield (680).[1] Ecgfrith was described as king of the Humberfolk'. After the loss ofLindsey (kingdom) which was south of theRiver Humber, the name became Northumbria inLatin isNorthanhymbrenis. It comes from theOld Englishbe northan Hymbre meaning 'to the north of the Humber'.[4] The name Northumbria was still used during the reigns of KingsCanute andEdward the Confessor.[1]William the Conqueror broke up Northumbria into several parts.[5]Yorkshire became the new name for the heartlands of the former kingdom.[1]
Northumbria became an earldom when the southern part of Northumbria (which had been Deira) was lost to theDanelaw.[6] The northern part (which had been Bernicia) was a kingdom for a short time but under the Danish kingdom it also became an earldom. Some of this land was claimed by both England and Scotland. The Earldom of Northumbria was later a part of England by the Anglo-ScottishTreaty of York in 1237. On the northern border,Berwick-upon-Tweed, which is north of the Tweed but had changed hands many times, was defined as subject to the laws of England by theWales and Berwick Act 1746. The land once part of Northumbria at its peak is now divided by modern administrative boundaries:
