Short answers, pulled from the story.
West Sussex is known for the South Downs, a chalk escarpment that crosses the county from east to west, dividing the rural interior from the coastal strip along the English Channel. Chichester Harbour, a ria on the western coast, is another defining geographical feature.
The oldest hominin remains known in Britain were found at Eartham Pit, Boxgrove, in West Sussex. Some of the earliest evidence of horses in Britain, dated to 500,000 BC, was also found at Boxgrove.
The Kingdom of Sussex was founded in AD 477, according to the Anglo-Saxon Chronicle, when Ælle arrived at a place called Cymenshore. The kingdom lasted until around AD 827, when it was absorbed into Wessex as an earldom.
Yes, West Sussex is identified as the sunniest county in the United Kingdom according to Met Office records. Over the 29 years to 2011, the county averaged 1,902 hours of sunshine per year, with Bognor Regis frequently recording the highest sunshine totals on the English mainland.
Chichester Cathedral was founded as a cathedral in 1075, when the seat of the bishop was moved from Selsey Abbey. It features both Norman and Gothic architecture, and the architectural historian Nikolaus Pevsner described it as "the most typical English Cathedral."
Crawley is the largest settlement in West Sussex, with an estimated population of 106,600. It is also the location of Gatwick Airport, which handled over 33 million passengers in 2011 and is the second-busiest airport in the United Kingdom.