Mercia

Mercia was one of the kingdoms of the Anglo-Saxon Heptarchy. Mercia dominated what would later become England for three centuries, subsequently going into a gradual decline while Wessex eventually conquered and united all the kingdoms into the Kingdom of England.
The kingdom was centred on the valley of the River Trent and its tributaries, in the region now known as the English Midlands. The court moved around the kingdom, and there was no fixed capital city. Early in its existence Repton seems to have been the location of an important royal estate. According to the Anglo-Saxon Chronicle, it was from Repton in 873–874 that the Great Heathen Army deposed the King of Mercia. Slightly earlier, King Offa seems to have favoured Tamworth. It was there where he was crowned and spent many a Christmas.
For 300 years (between 600 and 900), having annexed or gained submissions from five of the other six kingdoms of the Heptarchy (East Anglia, Essex, Kent, Sussex and Wessex), Mercia dominated England south of the River Humber: this period is known as the Mercian Supremacy. The reign of King Offa, who is best remembered for his Dyke that designated the boundary between Mercia and the Welsh kingdoms, is sometimes known as the "Golden Age of Mercia". 
Mercia was a pagan kingdom; King Peada converted to Christianity around 656, and Christianity was firmly established in the kingdom by the late 7th century. The Diocese of Mercia was founded in 656, with the first bishop, Diuma, based at Repton. After 13 years at Repton, in 669 the fifth bishop, Saint Chad, moved the bishopric to Lichfield, where it has been based since. In 691, the Diocese of Mercia became the Diocese of Lichfield. For a brief period between 787 and 799 the diocese was an archbishopric, although it was dissolved in 803. The current bishop, Michael Ipgrave, is the 99th since the diocese was established.
At the end of the 9th century, following the invasions of the Vikings and their Great Heathen Army, much of the former Mercian territory was absorbed into the Danelaw. At its height, the Danelaw included London, all of East Anglia and most of the North of England.
The final Mercian king, Ceolwulf II, died in 879; the kingdom appears to have thereby 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 again very briefly in 1016; however, by this time, it was viewed as a province within the Kingdom of England, not an independent kingdom.
Mercia is still used as a geographic designation, and the name is used by a wide range of organisations, including military units, public, commercial and voluntary bodies.
== In the early middle ages ==
=== 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", and the traditional interpretation is that the kingdom originated along the frontier between the native Welsh and the Anglo-Saxon invaders.
While its earliest boundaries will never be known, there is general agreement 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.