Wessex was, according to the Anglo-Saxon Chronicle founded by Cerdic and Cynric. The later expansion of Wessex influence to include present day Devon and Cornwall led to the increase in the power of the kings of Wessex. The Burghal system under Alfred the Great helped to prevent the overrunning of the south of England by the Danish invaders. Important settlements included Winchester which Alfred made the capital in 871.
There is some evidence that kingship in Wessex was not rigidly hereditary. The strongest candidate from the pool of the senior families was elected or forced his control on the lesser kings. The internal feuding produced by this may have delayed the rise of Wessex as a full kingdom, but this is conjecture. ...more info required...
Wessex was used by the English author, Thomas Hardy, as an imaginary county of southwestern England, the setting for most of his novels.
In an unusual move Prince Edward was made Earl of Wessex and Viscount Severn in honour of his marriage to Sophie Rhys-Jones. The title Earl of Wessex has not been in use for over 900 years. The last earl, King Harold, was famously killed at the Battle of Hastings in 1066.
There is a movement in modern day south-central England to create a regional cultural and political identity in Wessex. See Wessex Regionalist Party.