Cornwall

Cornwall was a county of England, and historically part of Damnonium. (TV: The Stones of Blood)

Geography
The county included the town of Stegmoor (AUDIO: Beachhead) and the villages of Bledoe, (PROSE: The Forgotten Son) Porthferiot, (COMIC: The Tansbury Experiment) and Treawtha. (COMIC: The Amateur)

History
Circa 16000 BC, a Tregannan survey team consisting of Sancreda and Scryfan landed at Cornwall. (AUDIO: The Spectre of Lanyon Moor)

Around 2000 BC, Cessair of Diplos arrived at Boscombe Moor using a segment of the Key to Time in the disguised form of the Great Seal of Diplos. She pretended to be a Celtic goddess, and was accompanied by Ogri. (TV: The Stones of Blood)

The First Doctor, Ben and Polly visited Cornwall in the 17th century. (TV: The Smugglers)

In the 20th century, the Third Doctor visited Downphilly to observe the launching of a space station. (COMIC: The Enemy from Nowhere) The Fourth Doctor and Romana I arrived at Boscombe Moor in search of one of the disguised segments of the Key to Time, eventually finding it in the possession of Cessair of Diplos. (TV: The Stones of Blood) He also visited Porthferiot while travelling with Sarah Jane Smith. (COMIC: The Tansbury Experiment)

An archaeological dig at Lanyon Moor in Cornwall was investigated by the Sixth Doctor in 2000, Evelyn Smythe and Brigadier Lethbridge-Stewart. (AUDIO: The Spectre of Lanyon Moor)

Whilst travelling alone and still in the apparent possession of his memories, the Eighth Doctor stopped off in a Cornish village. (PROSE: Rip Tide)

During the War in the Medusa Cascade in 2009, Alan and Maria Jackson were holidaying in Cornwall. (TV: The Stolen Earth)

In 2017, the Eighth Doctor visited Stegmoor and dealt with the survivor of a crashed Voord spaceship. (AUDIO: Beachhead)

Behind the scenes

 * The Second Doctor Volume Two (DWM 528) 1.jpg depicting the Second Doctor hosting a Twitch stream where a viewer by the name of "Duchess" mentions Cornwall.]]Michael Craze, who played Ben Jackson, was born in Cornwall.
 * According to the Doctor Who website, by 2006 Cornwall was an independent republic. This was also shown in the episode Boom Town in small print on a newspaper.
 * An illustration by Jamie Lenman for The Second Doctor: Volume Two, printed in DWM 528, featured the Second Doctor hosting a Twitch stream, where a viewer under the username "Duchess" sent the message "CORNWALL 2264 ❤️❤️❤️".