The Viking kingdom centered on York (Jorvik), seized by the Great Heathen Army in 866 and ruled by a succession of Norse and Hiberno-Norse kings (including Halfdan Ragnarsson, Guthfrith, and finally Eric Bloodaxe) until its final absorption into England.
Ended in 954 when Eric Bloodaxe, the last Norse king of York, was expelled and killed; Northumbria was thereafter incorporated directly into the Kingdom of England.
The atlas holds 2 border frames for Kingdom of Jorvik (Scandinavian York) — the shape you scrub through changes in 866 · 919.
By the archaeologist who led the Coppergate excavations that recovered Viking-Age York; dedicated to exactly this city/polity.