invasions of the Vikings and their Great Heathen Army, Danelaw absorbed much of the former Mercian territory. Danelaw at its height included London, all of East Anglia and most of the North of England. The final Mercian king, Ceolwulf II, died in 879 with the kingdom appearing to have lost its political independence. Initially, it was ruled by a lord or ealdorman under the overlordship of Alfred the Great, who styled himself "King of the Anglo-Saxons". The kingdom had a brief period of independence in the mid-10th century and in 1016, by which time it was viewed as a province with temporary independence. Wessex conquered and united all the kingdoms into the Kingdom of England. The kingdom became an earldom until 1071. History Early history Mercia's exact evolution at the start of the Anglo-Saxon era remains more obscure than that of Northumbria, Kent, or even Wessex. Mercia developed an effective political structure and adopted Christianity later than the other kingdoms. Archaeological surveys show that Angles settled the lands north of the River Thames by the 6th century. The name "Mercia" is Old English for "boundary folk" (see Welsh Marches), and the traditional interpretation is that the kingdom originated along the frontier between the native Welsh and the Anglo-Saxon invaders. However, Peter Hunter Blair argued an alternative interpretation: that they emerged along the frontier between Northumbria and the inhabitants of the Trent river valley. Although its earliest boundaries remain obscure, a general agreement persists that the territory that was called "the first of the Mercians" in the Tribal Hidage covered much of south Derbyshire, Leicestershire, Nottinghamshire, Northamptonshire, Staffordshire and northern Warwickshire. The earliest person named in any records as a king of Mercia is Creoda, said to have been the great-grandson of Icel. Coming to power around 584, he built a fortress at Tamworth which became the seat of Mercia's kings. His son Pybba succeeded him in 593. Cearl, a kinsman of Creoda, followed Pybba in 606; in 615, Cearl gave his daughter Cwenburga in marriage to Edwin, king of Deira, whom he had sheltered while he was an exiled prince. The Mercian kings were the only Anglo-Saxon Heptarchy ruling house known to claim a direct family link with a pre-migration Continental Germanic monarchy. Penda and the Mercian Supremacy The next Mercian king, Penda, ruled from about 626 or 633 until 655. Some of what is known about Penda comes from