Robert Harley, Earl of Oxford, who was born in Bow Street, Covent Garden, on the 5th of December 1661, was the eldest son of Sir Edward Harley, K.B., who was Governor of Dunkirk after the Restoration. Entering Parliament in 1689, in 1701 he was elected Speaker of the House of Commons; in 1710 he was appointed Chancellor of the Exchequer, and in 1711 he was created Earl of Oxford and Earl Mortimer, and made Lord High Treasurer, from which post he was dismissed in 1714. In 1713 he received the Order of the Garter. He was impeached by the House of Commons in 1715; acquitted without being brought to a trial in 1717, and died at his house in Albemarle Street, London, on the 21st of May 1724.

Harley was the greatest collector of his time, and formed a splendid library, which, at the time of his death, besides the printed books, contained more than six thousand volumes of manuscripts, and an immense number of charters, rolls, and deeds. This noble collection was inherited by Lord Oxford's son Edward, second Earl, by whom it was very considerably augmented in every department; and when he died in June 1741, the volumes of manuscripts amounted to seven thousand six hundred and thirty-nine volumes, exclusive of fourteen thousand two hundred and thirty-six original rolls, deeds, charters, and other legal documents. The printed books were estimated at about fifty thousand volumes, the pamphlets at about three hundred and fifty thousand, and the prints at forty-one thousand. In the Account of London Libraries, by Bagford and Oldys, it is stated:—

'For libraries in more expressly particular hands, the first and most universal in England, must be reckoned the Harleian, or Earl of Oxford's library, begun by his father and continued by himself. He has the rarest books of all countries, languages, and sciences, and the greatest number of any collector we ever had, in manuscript as well as in print, thousands of fragments, some a thousand years old; vellum books, some written over; all things especially respecting English History, personal as well as local, particular as well as general. He has a great collection of Bibles, etc., in all versions, and editions of all the first printed books, classics, and others of our own country, ecclesiastical as well as civil, by Caxton, Wynkyn de Worde, Pynson, Berthelet, Rastall, Grafton, and the greatest number of pamphlets and prints of English heads of any other person. Abundance of ledgers, chartularies, old deeds, charters, patents, grants, covenants, pedigrees, inscriptions, etc., and original letters of eminent persons, as many as would fill two hundred volumes; all the collections of his librarian Humphrey Wanley, of Stow, Sir Symonds D'Ewes, Prynne, Bishop Stillingfleet, John Bagford, Le Neve, and the flower of a hundred other libraries.'

The library was remarkably rich in early editions of the Greek and Latin classics (there were as many as one hundred and fifteen volumes of various works by Cicero printed in the fifteenth century), English early poetry and romances, and books of prints, sculpture and drawings. The collection of Caxtons was both large and fine, and it comprised the only perfect copy known of the Book of the Noble Histories of King Arthur, which, nearly a century and a half after the dispersion of the Harleian library, was purchased for nineteen hundred and fifty pounds, at the sale of the Earl of Jersey's books in 1885, by Mr. Quaritch for a New York collector.

The volumes in the library were all handsomely bound; mostly in red morocco, and tooled with a distinctive kind of ornamentation, which has since been known as the Harleian Style. This commonly consisted of a centrepiece, generally of a lozenge form, surrounded by a broad and elegant border. Eliot and Chapman were the binders of the greater portion of the books, at a cost, it is said, of upwards of eighteen thousand pounds.

Humphrey Wanley was for several years librarian to both the first and the second Earls, and he commenced the compilation of the catalogue of the manuscripts, which was finally completed by the Rev. Thomas Hartwell Horne in 1812. Among the Lansdowne manuscripts in the British Museum is a diary,[61] kept by Wanley, which contains much interesting information respecting the library. Some time after Wanley's decease, William Oldys was appointed librarian at a salary of two hundred pounds per annum.

The second Earl of Oxford had a passion for building and landscape gardening, as well as for collecting books, paintings and curiosities, and some years before his death these expensive tastes involved him in pecuniary difficulties. George Vertue, the eminent engraver, in one of his commonplace-books, now preserved in the British Museum,[62] thus feelingly refers to the embarrassed circumstances of the Earl:—'My good Lord, lately growing heavy and pensive in his affairs, which for some late years have mortify'd his mind.... This lately manifestly appeared in his change of complexion; his face fallen less; his colour and eyes turned yellow to a great degree; his stomach wasted and gone; and a dead weight presses continually, without sign of relief, on his mind.'

A fortnight after this was written Vertue had to lament his loss.

Lord Oxford died in Dover Street, London, on the 16th of June 1741, and on his decease the library became the property of Margaret, Duchess of Portland, the only daughter and heiress of the Earl, who sold the printed books to Mr. Thomas Osborne, the bookseller of Gray's Inn, for about thirteen thousand pounds. The manuscripts were purchased by Parliament in 1753 for the sum of ten thousand pounds, and were placed in the library of the British Museum four years later. The portraits, coins, and miscellaneous curiosities were sold by auction in March 1742.

Osborne bought Lord Oxford's books with a view of disposing of them by sale, and engaged Dr. Johnson and Oldys to compile a catalogue of them, which was printed in four volumes octavo in the years 1743-44. A fifth volume was issued in 1745, but this is nothing more than an enumeration of Osborne's unsold stock. Osborne also published in eight volumes quarto, 'The Harleian Miscellany: or, a Collection of Scarce, Curious, and Entertaining Pamphlets and Tracts, as well as in Manuscript as in Print, found in the late Earl of Oxford's library, interspersed with Historical, Political and Critical notes. London 1744-46.' This work, which was edited by Oldys, was republished by Thomas Park in 1808-12, with two supplemental volumes. A catalogue of the pamphlets contained in the Harleian Miscellany was also prepared by Oldys, and printed in a quarto volume, which appeared in 1746; and a Collection of Voyages and Travels, compiled from the Miscellany, was published in two volumes folio in 1745.