William Legge, 1st Earl of Dartmouth (1672-1750), only son of George Legge, 1st Baron Dartmouth , succeeded to his fathers barony in 1691. In 1702 he was appointed a member of the Board of Trade and Plantations, and eight years later he became Secretary of State for the Southern Department and joint keeper of the signet for Scotland. In 1711 he was created Viscount Lewisham and Earl of Dartmouth; in 1713 he exchanged his offices for that of Lord Privy Seal, which he held until the end of 1714. After a long period of retirement from public life he died on 15 December 1750. Dartmouths eldest son George Legge, Viscount Lewisham (c. 1703-1732), predeceased his father, leaving a son, William. Another son of the first earl was Henry Bilson-Legge, who later served as Chancellor of the Exchequer.

|- style="text-align: center;" | width="30%" |Preceded by:
John Robinson | width="40%" style="text-align: center;" |Lord Privy Seal
1713–1714 | width="30%" |Succeeded by:
The Marquess of Wharton