He became marquess of Hartington in 1858 and Duke of Devonshire in 1891.
He was a politician, and frequently held office in Liberal cabinets. By 1880 he was a recognized leader of the conservative (Whig) faction of the Liberal party with regard to social legislation. He led the Liberal Unionists who broke with Gladstone in 1886 over Home Rule for Ireland. In 1904 he left the Liberal Unionists because under Joseph Chamberlain they favoured the abandonment of free trade.
Debrett's Peerage, Baronetage and Knightage, London, 1907; http://www.bartleby.com (accessed 2004).