Mercia, sometimes spelled Mierce, was one of the kingdoms of the Anglo-Saxon heptarchy, in what is now England, in the region of the Midlands, with its heart in the valley of the River Trent and its tributary streams.
The Danes drove Burgred, the last king of Mercia from his kingdom in 874 and in 886, the eastern part of the kingdom became part of the Danelaw, while the western portion was occupied by Wessex.
The Danes appointed a Mercian thegn, Ceolwulf II, as king in 873 while the remaining independent section of Mercia was ruled by Aethelred, called an ealderman, not a king.