Before the Act of Union 1707, the barons of the shire or sheriffdom of Caithness elected commissioners to represent them in the unicameral Parliament of Scotland and in the Convention of Estates. After 1708, Caithness alternated with Buteshire in returning one member to the House of Commons of Great Britain and later to the House of Commons of the United Kingdom.
List of shire commissioners
1641: James Sinclair of Murkill
1648: Laird of Sandsyde (Innes)
1649–50: Sir John Sinclair of Dunbeath
1661: James Sinclair of Murkill
1661–63: William Sinclair of Latheron and Dunbeath
1665 convention: James Innes of Sandsyde
1667 convention, 1669–74: no representation
1678 convention: William Dunbar of Hempriggs
1678 convention: John Sinclair of Ulbster
1681–82: George Sinclair of Bilbster
1685–86, 1702-05: Sir George Sinclair of Clyth (died c.1705)
1689–93: James Sinclair of Freswick (died c.1693)
1693–95: Alexander Manson of Bridgend
1695–1701: Patrick Murray of Pennyland
1703–07: Sir James Sinclair of Dunbeath
1706–07: Sir James Dunbar of Hempriggs