John Spencer was previously created Baron Spencer of Althorp and Viscount Spencer in 1761. In 1765, he was advanced to the Viscounty of Althorp and the Earldom of Spencer. He served as the High Steward of St. Albans. On 20 December 1755, he married Georgiana [d. 1814], elder daughter of Right Hon. Stephen Poyntz of Midgham, Berkshire. Their three children were Georgiana, Henrietta Frances, and George John (who succeeded his father as 2nd Earl Spencer).
Cooper, Douglas, ed. Great Family Collections. New York, 1965:197-240