William Hugh Elliot Murray Kynynmound was the eldest surviving son of the 2nd Earl of Minto, who was styled Viscount Melgund from 1814 and succeeded as Earl of Minto in 1859. He was Member of Parliament for Hythe, 1837-1841, for Greenock, 1847-1852, and for Clackmannan and Kinross, 1857-1859; served as chairman of the Lunacy Commission, Scotland, 1857. As an active back-bench MP and peer, who was closely related to some of the leading political figures of his time - he was, for example, the father of Arthur Elliot, the brother of Sir Henry George Elliot, and the brother-in-law of the 1st Earl Russell. The 3rd Earl of Minto's correspondence and papers contain much material concerning British politics and Scottish affairs the Victorian era. The election and constituency correspondence is especially rich, and there is abundant material concerning Church of Scotland affairs and the education question in Scotland.
In 1844 the 3rd Earl of Minto married Emma Eleanor Elizabeth ('Nina') Hislop, daughter of General Sir Thomas Hislop, and granddaughter of Hugh Elliot. Her correspondence contains much material relating to her publications, as well as to her historical and literary interests in general.
William Hugh Elliot Murray Kynymound, 3rd Earl of Minto is referred to throughout this section simply as 'the 3rd Earl of Minto'. His wife is referred to as 'the Countess of Minto'.