Although modern usage outside of the county itself now rarely refers to Devon as "Devonshire", the title remained "Duke of Devonshire". Despite the territorial designation of the dukedom and the subsidiary title of the earldom of Devonshire, the family estates are centred in Derbyshire. The title "Duke of Devonshire" should not be confused with the ancient title of Earl of Devon.
Uniquely, every Duke of Devonshire has so far been appointed a Knight of the Garter, except (as of 2018) the present one.
The Cavendish family descends from Sir John Cavendish, who took his name from the village of Cavendish, Suffolk, where he held an estate in the 14th century. He served as Chief Justice of the King's Bench from 1372 to 1381, and was killed in the Peasants' Revolt in 1381. Two of his great-grandsons were George Cavendish, Thomas Cardinal Wolsey's biographer, and George's younger brother Sir William Cavendish. Sir William gained great wealth from his position in the Exchequer and also (allegedly) from unfairly taking advantage of the dissolution of the Monasteries. He married (1547) as his third wife the famous Bess of Hardwick, with whom he had eight children. One of their sons, Sir Charles Cavendish (1553–1617), was the father of William Cavendish, 1st Duke of Newcastle-upon-Tyne (1592-1676, see the Duke of Newcastle-upon-Tyne for more information on this branch of the family), while another son, Henry Cavendish, was the ancestor of the Barons Waterpark. Yet another son, William Cavendish (1552-1626), was a politician and a supporter of the colonization of Virginia. In 1605 he was raised to the peerage as Baron Cavendish, of Hardwicke in the County of Derby, and in 1618 he was further honoured when he was made Earl of Devonshire. Both titles are in the Peerage of England.
He was succeeded by his eldest son, William Cavendish, 2nd Earl of Devonshire, who served as Lord-Lieutenant of Derbyshire and was a patron of the philosopher Thomas Hobbes (1588–1679). On his early death in 1628 the titles passed to his son, William Cavendish, 3rd Earl of Devonshire, who also served as Lord-Lieutenant of Derbyshire. He was succeeded by his son, the fourth Earl. He was a strong supporter of the Glorious Revolution of 1688 and later served under William III and Mary II as Lord Steward of the Household. In 1694 he was created Marquess of Hartington and Duke of Devonshire in the Peerage of England. He was succeeded by his eldest son, the second Duke, who held political office as Lord President of the Council and Lord Privy Seal and was also Lord-Lieutenant of Devonshire. His eldest son, the third Duke, served as Lord Privy Seal, as Lord Steward of the Household and (from 1737 to 1745) as Lord-Lieutenant of Ireland.
On his death the titles passed to his eldest son, the fourth Duke, who was a prominent politician. He was summoned to the House of Lords through a writ of acceleration in his father's junior title of Baron Cavendish, of Hardwicke in 1751 and served as First Lord of the Treasury and titular Prime Minister of Great Britain from 1756 to 1757. Devonshire married Charlotte Boyle, 6th Baroness Clifford, daughter of the famous architect Richard Boyle, 3rd Earl of Burlington (on whose death in 1753 the earldom of Burlington became extinct). Their third and youngest son Lord George Cavendish was recreated Earl of Burlington in 1831. Devonshire was succeeded by his eldest son, William Cavendish, who became the fifth Duke of Devonshire. He had already succeeded his mother as seventh Baron Clifford in 1754. He served as Lord-Lieutenant of Derbyshire from 1782 to 1811 but is best remembered for his first marriage (1774) to Lady Georgiana Spencer (1757–1806), the celebrated beauty and society hostess.