The Anglo-Saxon settlement of Britain resulted in the partial assimilation of Dumnonia into the kingdom of Wessex in the eighth and ninth centuries, and the western boundary with Cornwall was set at the Tamar by king Æthelstan in 936.

[citation needed] William Camden, in his 1607 edition of Britannia, described Devon as being one part of an older, wider country that once included Cornwall: THAT region which, according to the Geographers, is the first of all Britaine, and, growing straiter still and narrower, shooteth out farthest into the West, [...] was in antient time inhabited by those Britans whom Solinus called Dumnonii, Ptolomee Damnonii [...] For their habitation all over this Countrey is somewhat low and in valleys, which manner of dwelling is called in the British tongue Dan-munith, in which sense also the Province next adjoyning in like respect is at this day named by the Britans Duffneit, that is to say, Low valleys.

One erroneous theory is that the shire suffix is due to a mistake in the making of the original letters patent for the Duke of Devonshire, resident in Derbyshire.

There are references to both Defnas and Defenasċīre in Anglo-Saxon texts from before 1000 CE (the former is a name for the "people of Devon" and the latter would mean 'Shire of the Devonians'),[8] which translates to modern English as Devonshire.

Danish raids also occurred sporadically along many coastal parts of Devon between around 800AD and just before the time of the Norman conquest, including the silver mint at Hlidaforda Lydford in 997 and Taintona (a settlement on the Teign estuary) in 1001.

In South Devon the landscape consists of rolling hills dotted with small towns, such as Dartmouth, Ivybridge, Kingsbridge, Salcombe, and Totnes.

The measures are so called either from the occasional presence of a soft, sooty coal, which is known in Devon as culm, or from the contortions commonly found in the beds.

Smaller outcrops of younger rocks also exist, such as Cretaceous chalk cliffs at Beer Head and gravels on Haldon, plus Eocene and Oligocene ball clay and lignite deposits in the Bovey Basin, formed around 50 million years ago under tropical forest conditions.

It is also the only place in mainland Britain where the sand crocus (Romulea columnae) can be found – at Dawlish Warren, and is home to all six British native land reptile species, partly as a result of some reintroductions.

Devon is divided into two Watsonian vice-counties: north and south, the boundary being an irregular line approximately across the higher part of Dartmoor and then along the canal eastwards.

[32] In January 2024, plans were announced to plant over 100,000 trees in northern Devon to support Celtic rainforests, which are cherished yet at risk ecosystems in the UK.

Led by the National Trust and with the assistance of volunteers and community groups, the initiative will focus on locations in Exmoor, Woolacombe, Hartland, and Arlington Court.

[37] Historically Devon was divided into 32 hundreds:[38] Axminster, Bampton, Black Torrington, Braunton, Cliston, Coleridge, Colyton, Crediton, East Budleigh, Ermington, Exminster, Fremington, Halberton, Hartland, Hayridge, Haytor, Hemyock, Lifton, North Tawton and Winkleigh, Ottery, Plympton, Roborough, Shebbear, Shirwell, South Molton, Stanborough, Tavistock, Teignbridge, Tiverton, West Budleigh, Witheridge, and Wonford.

Rural market towns in the county include Barnstaple, Bideford, Honiton, Newton Abbot, Okehampton, Tavistock, Totnes and Tiverton.

The position of churches bearing his name, including one within the old Roman walls of Exeter, are nearly always near the coast, as in those days travelling was done mainly by sea.

From the late sixteenth century onwards, zealous Protestantism – or 'puritanism' – became increasingly well-entrenched in some parts of Devon, while other districts of the county remained much more conservative.

The seal contained three shields depicting the arms of Exeter along with those of the first chairman and vice-chairman of the council (Lord Clinton and the Earl of Morley).

The main part of the shield displays a red crowned lion on a silver field, the arms of Richard Plantagenet, Earl of Cornwall.

[57] Devon has a variety of festivals and traditional practices, including the traditional orchard-visiting Wassail in Whimple every 17 January, and the carrying of flaming tar barrels in Ottery St. Mary, where people who have lived in Ottery for long enough are called upon to celebrate Bonfire Night by running through the village (and the gathered crowds) with flaming barrels on their backs.

[58] Berry Pomeroy still celebrates Queene's Day for Elizabeth I. Devon's total economic output in 2019 was over £26 billion, larger than either Manchester, or Edinburgh.

[60] Like neighbouring Cornwall to the west, historically Devon has been disadvantaged economically compared to other parts of Southern England, owing to the decline of a number of core industries, notably fishing, mining, and farming, but it is now significantly more diverse.

The pandemic negatively affected the economy during 2020 and early 2021; an August 2021 report states that "the immediate economic impacts of COVID-19 for the County as a whole [was] as severe as any in living memory".

[62] in 2014 to 2016, the attractive lifestyle of the area was drawing in new industries which are not heavily dependent upon geographical location;[63][64] Dartmoor, for instance, has recently seen a significant rise in the percentage of its inhabitants involved in the digital and financial services sectors.

Plymouth hosts the head office and first ever store of The Range, the only major national retail chain headquartered in Devon.

Incomes in much of the South Hams and in villages surrounding Exeter and Plymouth are close to, or above the national average, but there are also areas of severe deprivation, with earnings in some places among the lowest in the UK.

One club – Exeter Chiefs – play in the Aviva Premiership, winning the title in 2017 for the first time in their history after beating Wasps RFC in the final 23–20.

[83] Motorcycle speedway is also supported in the county, with both the Exeter Falcons and Plymouth Gladiators succeeding in the National Leagues in recent years.

[85] Another famous mariner and Devonian was Robert Falcon Scott, the leader of the unfortunate Terra Nova Expedition to reach the geographical South Pole.

Chris Dawson, the billionaire owner of retailer The Range was born in Devon, where his business retains its head office in Plymouth.

Matt Bellamy, Dominic Howard and Chris Wolstenholme from the English group Muse all grew up in Devon and formed the band there.