Clifton, Dartmouth and Hardness were three towns clustered round the mouth of the River Dart in southern Devon; all three are within the modern town of Dartmouth. The borough as first represented in 1298 seems to have included only the town of Dartmouth, but at the next return of members in 1350–1351 it also included Clifton; Hardness is first mentioned in 1553, though may have been included earlier. The boundaries by the 19th century included the whole of Dartmouth St Petrox and St Saviour parishes, and part of Townstall parish.
Dartmouth by the end of the 18th century was a prosperous small port, depending mainly on fishing but also with some shipbuilding interests; but the bulk of the inhabitants had little voice in the choice of its Members of Parliament. After a decision by Parliament that followed a disputed election in 1689, the right to vote in Dartmouth rested with the Corporation, which appointed its own successors, and with the freemen of the borough, who were made by the Corporation. This amounted to a total of 71 voters in 1832, although only 53 of these were resident; virtually all were officers of the custom house or other government employees.
This franchise meant that once control was gained of the borough it was easy to retain indefinitely. Around the turn of the 18th century, the Herne family had almost total control, but in the mid-to-late 18th and early 19th century, control had passed to the government and Dartmouth was considered a safe seat for the party in power, returning one member at the nomination of the Treasury and one of the Admiralty. (Even this control had its limits however – Namier and Brooke quote letters to show that when a vacancy arose in 1757, the government had to abandon their original intention of nominating a soldier, and instead acceded to the corporation's demand for a naval candidate.) The Holdsworth family managed the government's interests in the borough, and generally had first refusal on one of the seats. Indeed, the Holdsworths were sufficiently influential to defy the government on occasion, as in 1780 when Arthur Holdsworth arranged the re-election of the popular but opposition-supporting naval hero Lord Howe to one seat while taking the other for himself – no government candidates stood against them, and both Howe and Holdsworth voted with the opposition in the new Parliament.
At the time of the Great Reform Act, the 1831 census showed that there were 611 houses in the borough but a population of 4,447. Dartmouth was allowed to keep one of its two MPs, and the boundaries were extended slightly to include the whole of Townstall parish and part of Stoke Fleming, bringing the population up to 4,662.
^Booth was originally declared elected, but on petition the House of Commons decided that some of his voters had not validly been made Freemen, and were therefore ineligible to vote; Booth's opponent, Herne, was consequently declared elected in his place. (House of Commons Journal, 28 November 1689 )
^Sir Joseph Herne died 26 February 1699. There is apparently no record of a writ for a by-election being issued, and the seat may have remained vacant for the remainder of the Parliament
^Succeeded as the 4th Viscount Howe (in the Peerage of Ireland, July 1758. Rear Admiral 1770, Vice Admiral 1775, Admiral 1782