The dialect was spoken from the Humber, now within England, to the Firth of Forth, now within Scotland. During the Viking invasions of the 9th century, Northumbrian came under the influence of the languages of the Viking invaders.
The Viking invasion forced the dialect to split in two. The southern Northumbrian dialect was heavily influenced by Norse. The northern Northumbrian dialect not only retained a lot of the Old English words (replaced in the south by Norse words) but was also a strong influence on the development of the English language in northern England, especially the dialects of modern North east England and Scotland.
The north-south split was around the Tees river.
FADER USÆR ðu arðin heofnu
Sie gehalgad NOMA ÐIN.
Tocymeð RÍC ÐIN.
Sie WILLO ÐIN
suæ is in heofne and in eorðo.
HLAF USERNE of'wistlic sel ús todæg,
and f'gef us SCYLDA USRA,
suæ uoe f'gefon SCYLDGUM USUM.
And ne inlæd usih in costunge,
ah is in heofne and in eorðo.
Other examples of this dialect are the Runes on the Ruthwell Cross from the Dream of the Rood.