Lady Strafford (1715-1785) was the second of five daughters born to John Campbell, 2nd Duke of Argyll. Following her marriage in 1741 to William Wentworth, 2nd Earl of Strafford, the couple became part of a social set that included luminaries such as Horace Walpole. Walpole particularly considered the countess to be a "vast beauty" whose charms he immortalized in a poem published in 1765. Entries in Reynolds' sitters book reveal that this painting was executed over several sittings between 1758 and 1759. That it was subsequently reproduced by at least four engravers indicates that painter, portrait, and sitter were all held in high regard.