The title of Earl of Sunderland was created in the Peerage of England in 1643. In 1733, the 5th Earl succeeded to the title of Duke of Marlborough, with which title the earldom has ever since been merged, and generally used as a courtesy title for the heir apparent to the heir apparent of the Dukedom. The Earls bore the subsidiary title of Baron Spencer (1603).
The title had also briefly existed in a previous creation for the Lord Scrope of Bolton in 1627, but became extinct upon the 1st Earl's death three years later.
Having succeeded to the peerage in 1702, the earl was one of the commissioners for the union between England and Scotland, and in 1705 he was sent to Vienna as envoy extraordinary.
Sunderland continued to take part in public life, and was active in communicating with the court of Hanover about the steps to be taken in view of the approaching death of the queen.
Sunderland was especially interested in the proposed peerage bill, a measure designed to limit the number of members of the House of Lords, but this was defeated owing partly to the opposition of Sir Robert Walpole.