Ferguson was born on 28 July 1837, the elder son of Joseph Ferguson (1794-1880) of Carlisle, by his wife Margaret (died 2 November 1841), daughter of Silas Saul of Carlisle. The family settled in Carlisle about 1700, and founded the cotton industry in the city. He was educated at Carlisle Grammar School, entered Shrewsbury School in 1853, and was admitted at St. John's College, Cambridge, as a scholar on 14 March 1856. He graduated B.A. in 1860, M.A. in 1863, and LL.M. in 1864. He was admitted a student of Lincoln's Inn on 11 October 1858, and was called to the bar on 13 June 1862, when he commenced practice as an equity draughtsman and conveyancer, and joined the northern circuit.
He was examiner of civil law for Cambridge University in 1868-9. From January 1871 to June 1872 he travelled in Egypt, Australia, and America for the sake of his health, and on his return gave the public an account of his experiences in a series of letters in the Carlisle Patriot, which were reprinted, with the addition of Leaves from a Theban Guide Book, as Moss gathered by a Rolling Stone (Carlisle, 1873).
After his return Ferguson settled at Carlisle, and devoted himself to the study of local antiquities. He associated with others of similar tastes, including Michael Waistell Taylor, Robert Harkness, and Sir George Floyd Duckett. Already in 1866 he had assisted to found the Cumberland and Westmorland Archæological and Antiquarian Society, and from 1868 he edited the society's Transactions. Under his guidance nearly the whole of Cumberland and Westmorland were explored, and record made of castles, churches, houses, manuscripts, and old customs. On the death of Canon James Simpson in 1886, Ferguson succeeded him as president of the society. His own special period was that of the Roman occupation of Cumberland, and under his care the collection of Roman antiquities at the city museum, Tullie House, became extensive.
Ferguson was made a magistrate of the county of Cumberland in 1872, and a member of the Carlisle city bench in 1881. In 1886, he was elected chairman of quarter sessions. He was elected a member of the Carlisle city council in 1878, and took advantage of his position to gain access to the ancient muniments of the city, many of which he published. In 1881-2 he was chosen mayor and was re-elected in the following year. He was a strong supporter of the city privileges, and when county councils were instituted in January 1889 and he was elected a member for Carlisle, he lost no opportunity of urging the rights of the city. He was one of the promoters of the project by which Tullie House was taken for the use of the city, with a museum, a public library, a school of science and art, and art galleries. Under his influence William Jackson was induced to bequeath to the city the Jackson library, a valuable collection of local literature. In recognition of his services the corporation conferred upon him the honorary freedom of the city in 1896.
In 1887 Harvey Goodwin, bishop of Carlisle, appointed Ferguson chancellor of the diocese, a post that had not previously been held by a layman. Ferguson was elected a fellow of the Society of Antiquaries of London on 1 March 1877, member of the Royal Archæological Institute about 1878 and a fellow of the Society of Antiquaries of Scotland in 1880. In 1895 he was admitted an honorary member of the Glasgow Archæological Association. He was a vice-president of the Royal Archæological Institute and of the Surtees Society.
Ferguson died at Carlisle on 3 March 1900, at his residence, 74 Lowther Street. His portrait, painted by Mr. Sephton, was presented to him by the corporation of Carlisle in 1896. A replica hangs in the vestibule of Tullie House.
In August 1867 he married, at Kew, Georgiana Fanny Shelley, eldest daughter of Spencer Shelley of Richmond House, Kew, principal clerk of the treasury, and granddaughter of Sir John Shelley, 6th Baronet. He was separated from her in 1872, and divorced her in December 1877. By her he had one son, Spencer Charles Ferguson, who served as an officer in the Northumberland Fusiliers, and one daughter, Margaret Josephine Ferguson, who married in 1896 the Rev. Frederick Luke Holland Millard, vicar of Aspatria.
Ferguson's first literary production was a series of articles on Early Cumberland and Westmorland Friends in the Carlisle Journal, a number of biographical sketches of leading quakers in the two counties. They were republished in book form in 1871 (London), and were followed in the same year by Cumberland and Westmorland M.P.'s from the Restoration to the Reform Bill of 1867 (London), a book containing a full political history of the counties. He also wrote:
Ferguson edited a series of works for the Cumberland and Westmorland Archæological Society:
Ferguson contributed a biographical notice of Michael Waistell Taylor to Taylor's Old Manorial Halls of Cumberland and Westmorland, 1892, and a preface to Hugh Alexander Macpherson's Vertebrate Fauna of Lakeland, 1892. He was a contributor to the Antiquary, Reliquary, and the Archæologia of the Society of Antiquaries.
This article incorporates text from a publication now in the public domain: Lee, Sidney, ed. (1901). "Ferguson, Richard Saul". Dictionary of National Biography (1st supplement). 2. London: Smith, Elder & Co.