The Kingdom of Essex reference article from the English Wikipedia on 24-Apr-2004
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Kingdom of Essex

Helping orphans the way you would do it
The Kingdom of the East Seaxe (one of the seven traditional kingdoms of the so-called Anglo-Saxon Heptarchy) was founded around 500 AD, occupying territory to the north and east of London. Around 825 AD, the kingdom was merged with Wessex, and was eventually ceded by Wessex under the Treaty of Wedmore to the Danelaw control of the Danish kingdom of East Anglia. Essex is now a county in England.

Here are the Kings of Essex; the dates, names and achievements, like those of most early rulers in all countries of the Heptarchy, remain conjectural. This dynasty claimed descent from the god Seaxneat, not the god Woden (of which the other Saxon tribes claimed descent). This list of kings may omit whole generations.

Sigered was the last king of Essex, and he ceded the kingdom to Egbert of Wessex.